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 $114.25   4.188%   $119.0348   $119.03   $119.05   $119.00  
  Purchase #2 $65.53   4.103%   $68.2187   $68.22   $68.20   $68.20  
  Purchase #3 $159.33   8.755%   $173.2793   $173.28   $173.30   $173.30  
  Purchase #4 $75.43   13.665%   $85.7375   $85.74   $85.75   $85.70  
  Purchase #5 $177.97   9.726%   $195.2794   $195.28   $195.30   $195.30  
  Purchase #6 $200.85   13.707%   $228.3805   $228.38   $228.40   $228.40  
  Purchase #7 $208.73   10.647%   $230.9535   $230.95   $230.95   $231.00  
  7 purchase totals = $1,002.09       $1,100.8837   $1,100.88   $1,100.95   $1,100.90