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 $24.95   5.209%   $26.2496   $26.25   $26.25   $26.20  
  Purchase #2 $144.59   9.706%   $158.6239   $158.62   $158.60   $158.60  
  Purchase #3 $76.36   11.733%   $85.3193   $85.32   $85.30   $85.30  
  Purchase #4 $138.51   9.683%   $151.9219   $151.92   $151.90   $151.90  
  Purchase #5 $161.45   10.330%   $178.1278   $178.13   $178.15   $178.10  
  Purchase #6 $62.57   6.640%   $66.7246   $66.72   $66.70   $66.70  
  Purchase #7 $184.47   9.819%   $202.5831   $202.58   $202.60   $202.60  
  7 purchase totals = $792.90       $869.5502   $869.54   $869.50   $869.40