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 $84.45   12.830%   $95.2849   $95.28   $95.30   $95.30  
  Purchase #2 $169.96   11.383%   $189.3065   $189.31   $189.30   $189.30  
  Purchase #3 $57.38   7.451%   $61.6554   $61.66   $61.65   $61.70  
  Purchase #4 $200.95   9.847%   $220.7375   $220.74   $220.75   $220.70  
  Purchase #5 $234.83   11.743%   $262.4061   $262.41   $262.40   $262.40  
  Purchase #6 $86.92   6.282%   $92.3803   $92.38   $92.40   $92.40  
  Purchase #7 $208.59   9.120%   $227.6134   $227.61   $227.60   $227.60  
  7 purchase totals = $1,043.08       $1,149.3841   $1,149.39   $1,149.40   $1,149.40