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 $113.65   10.839%   $125.9685   $125.97   $125.95   $126.00  
  Purchase #2 $87.77   12.211%   $98.4876   $98.49   $98.50   $98.50  
  Purchase #3 $64.64   5.534%   $68.2172   $68.22   $68.20   $68.20  
  Purchase #4 $22.37   9.720%   $24.5444   $24.54   $24.55   $24.50  
  Purchase #5 $150.96   4.824%   $158.2423   $158.24   $158.25   $158.20  
  Purchase #6 $209.97   6.756%   $224.1556   $224.16   $224.15   $224.20  
  Purchase #7 $28.91   6.827%   $30.8837   $30.88   $30.90   $30.90  
  7 purchase totals = $678.27       $730.4993   $730.50   $730.50   $730.50