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 $44.40   5.530%   $46.8553   $46.86   $46.85   $46.90  
  Purchase #2 $236.57   11.485%   $263.7401   $263.74   $263.75   $263.70  
  Purchase #3 $162.35   4.177%   $169.1314   $169.13   $169.15   $169.10  
  Purchase #4 $41.95   13.167%   $47.4736   $47.47   $47.45   $47.50  
  Purchase #5 $11.42   11.298%   $12.7102   $12.71   $12.70   $12.70  
  Purchase #6 $96.39   8.587%   $104.667   $104.67   $104.65   $104.70  
  Purchase #7 $180.38   5.817%   $190.8727   $190.87   $190.85   $190.90  
  7 purchase totals = $773.46       $835.4503   $835.45   $835.40   $835.50