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 $89.37   5.417%   $94.2112   $94.21   $94.20   $94.20  
  Purchase #2 $15.58   11.571%   $17.3828   $17.38   $17.40   $17.40  
  Purchase #3 $94.44   3.602%   $97.8417   $97.84   $97.85   $97.80  
  Purchase #4 $207.77   4.257%   $216.6148   $216.61   $216.60   $216.60  
  Purchase #5 $52.61   5.388%   $55.4446   $55.44   $55.45   $55.40  
  Purchase #6 $18.31   13.206%   $20.728   $20.73   $20.75   $20.70  
  Purchase #7 $213.67   5.138%   $224.6484   $224.65   $224.65   $224.60  
  7 purchase totals = $691.75       $726.8715   $726.86   $726.90   $726.70