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 $95.53   6.801%   $102.027   $102.03   $102.05   $102.00  
  Purchase #2 $84.37   8.166%   $91.2597   $91.26   $91.25   $91.30  
  Purchase #3 $57.32   4.468%   $59.8811   $59.88   $59.90   $59.90  
  Purchase #4 $164.68   13.576%   $187.037   $187.04   $187.05   $187.00  
  Purchase #5 $155.55   9.142%   $169.7704   $169.77   $169.75   $169.80  
  Purchase #6 $41.48   13.578%   $47.1122   $47.11   $47.10   $47.10  
  Purchase #7 $197.88   9.391%   $216.4629   $216.46   $216.45   $216.50  
  7 purchase totals = $796.81       $873.5503   $873.55   $873.55   $873.60