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 $91.54   4.145%   $95.3343   $95.33   $95.35   $95.30  
  Purchase #2 $12.49   7.252%   $13.3958   $13.40   $13.40   $13.40  
  Purchase #3 $48.62   7.152%   $52.0973   $52.10   $52.10   $52.10  
  Purchase #4 $105.28   7.624%   $113.3065   $113.31   $113.30   $113.30  
  Purchase #5 $211.72   6.452%   $225.3802   $225.38   $225.40   $225.40  
  Purchase #6 $170.92   5.659%   $180.5924   $180.59   $180.60   $180.60  
  Purchase #7 $71.26   6.637%   $75.9895   $75.99   $76.00   $76.00  
  7 purchase totals = $711.83       $756.0960   $756.10   $756.15   $756.10