Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $162.37   8.399%   $176.0075   $176.01   $176.00   $176.00  
  Purchase #2 $141.50   13.226%   $160.2148   $160.21   $160.20   $160.20  
  Purchase #3 $174.63   12.808%   $196.9966   $197.00   $197.00   $197.00  
  Purchase #4 $192.83   4.370%   $201.2567   $201.26   $201.25   $201.30  
  Purchase #5 $195.41   11.351%   $217.591   $217.59   $217.60   $217.60  
  Purchase #6 $146.36   6.828%   $156.3535   $156.35   $156.35   $156.40  
  Purchase #7 $214.67   11.480%   $239.3141   $239.31   $239.30   $239.30  
  7 purchase totals = $1,227.77       $1,347.7342   $1,347.73   $1,347.70   $1,347.80