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 $88.26   4.471%   $92.2061   $92.21   $92.20   $92.20  
  Purchase #2 $39.48   4.298%   $41.1769   $41.18   $41.20   $41.20  
  Purchase #3 $12.88   13.594%   $14.6309   $14.63   $14.65   $14.60  
  Purchase #4 $197.26   3.157%   $203.4875   $203.49   $203.50   $203.50  
  Purchase #5 $238.31   12.151%   $267.267   $267.27   $267.25   $267.30  
  Purchase #6 $69.73   6.721%   $74.4166   $74.42   $74.40   $74.40  
  Purchase #7 $220.83   5.332%   $232.6047   $232.60   $232.60   $232.60  
  7 purchase totals = $866.75       $925.7897   $925.80   $925.80   $925.80