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 $190.88   8.410%   $206.933   $206.93   $206.95   $206.90  
  Purchase #2 $117.45   6.563%   $125.1582   $125.16   $125.15   $125.20  
  Purchase #3 $169.49   12.120%   $190.0322   $190.03   $190.05   $190.00  
  Purchase #4 $171.95   6.190%   $182.5937   $182.59   $182.60   $182.60  
  Purchase #5 $47.32   9.409%   $51.7723   $51.77   $51.75   $51.80  
  Purchase #6 $193.68   3.817%   $201.0728   $201.07   $201.05   $201.10  
  Purchase #7 $240.96   11.389%   $268.4029   $268.40   $268.40   $268.40  
  7 purchase totals = $1,131.73       $1,225.9651   $1,225.95   $1,225.95   $1,226.00