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 $92.66   9.364%   $101.3367   $101.34   $101.35   $101.30  
  Purchase #2 $55.43   5.491%   $58.4737   $58.47   $58.45   $58.50  
  Purchase #3 $26.39   7.490%   $28.3666   $28.37   $28.35   $28.40  
  Purchase #4 $94.46   8.118%   $102.1283   $102.13   $102.15   $102.10  
  Purchase #5 $143.87   3.475%   $148.8695   $148.87   $148.85   $148.90  
  Purchase #6 $233.92   4.411%   $244.2382   $244.24   $244.25   $244.20  
  Purchase #7 $247.94   5.762%   $262.2263   $262.23   $262.25   $262.20  
  7 purchase totals = $894.67       $945.6393   $945.65   $945.65   $945.60