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 $194.54   6.276%   $206.7493   $206.75   $206.75   $206.70  
  Purchase #2 $185.82   7.300%   $199.3849   $199.38   $199.40   $199.40  
  Purchase #3 $56.76   7.123%   $60.803   $60.80   $60.80   $60.80  
  Purchase #4 $239.74   9.102%   $261.5611   $261.56   $261.55   $261.60  
  Purchase #5 $222.96   12.290%   $250.3618   $250.36   $250.35   $250.40  
  Purchase #6 $40.60   13.357%   $46.0229   $46.02   $46.00   $46.00  
  Purchase #7 $188.66   6.395%   $200.7248   $200.72   $200.70   $200.70  
  7 purchase totals = $1,129.08       $1,225.6078   $1,225.59   $1,225.55   $1,225.60