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 $201.58   4.265%   $210.1774   $210.18   $210.20   $210.20  
  Purchase #2 $173.91   11.688%   $194.2366   $194.24   $194.25   $194.20  
  Purchase #3 $149.87   7.146%   $160.5797   $160.58   $160.60   $160.60  
  Purchase #4 $243.25   5.627%   $256.9377   $256.94   $256.95   $256.90  
  Purchase #5 $111.63   8.660%   $121.2972   $121.30   $121.30   $121.30  
  Purchase #6 $177.46   4.354%   $185.1866   $185.19   $185.20   $185.20  
  Purchase #7 $68.72   10.498%   $75.9342   $75.93   $75.95   $75.90  
  7 purchase totals = $1,126.42       $1,204.3494   $1,204.36   $1,204.45   $1,204.30