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 $190.68   5.422%   $201.0187   $201.02   $201.00   $201.00  
  Purchase #2 $244.40   13.324%   $276.9639   $276.96   $276.95   $277.00  
  Purchase #3 $139.90   6.522%   $149.0243   $149.02   $149.00   $149.00  
  Purchase #4 $172.30   8.425%   $186.8163   $186.82   $186.80   $186.80  
  Purchase #5 $159.70   9.191%   $174.378   $174.38   $174.40   $174.40  
  Purchase #6 $194.77   11.480%   $217.1296   $217.13   $217.15   $217.10  
  Purchase #7 $248.71   5.354%   $262.0259   $262.03   $262.05   $262.00  
  7 purchase totals = $1,350.46       $1,467.3567   $1,467.36   $1,467.35   $1,467.30