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 $142.26   7.551%   $153.0021   $153.00   $153.00   $153.00  
  Purchase #2 $175.77   12.133%   $197.0962   $197.10   $197.10   $197.10  
  Purchase #3 $165.47   13.701%   $188.141   $188.14   $188.15   $188.10  
  Purchase #4 $159.85   11.814%   $178.7347   $178.73   $178.75   $178.70  
  Purchase #5 $214.93   11.534%   $239.72   $239.72   $239.70   $239.70  
  Purchase #6 $163.68   11.296%   $182.1693   $182.17   $182.15   $182.20  
  Purchase #7 $74.30   3.639%   $77.0038   $77.00   $77.00   $77.00  
  7 purchase totals = $1,096.26       $1,215.8671   $1,215.86   $1,215.85   $1,215.80