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 $208.95   11.110%   $232.1643   $232.16   $232.15   $232.20  
  Purchase #2 $115.55   8.829%   $125.7519   $125.75   $125.75   $125.80  
  Purchase #3 $198.44   4.336%   $207.0444   $207.04   $207.05   $207.00  
  Purchase #4 $152.53   9.500%   $167.0204   $167.02   $167.00   $167.00  
  Purchase #5 $99.42   11.258%   $110.6127   $110.61   $110.60   $110.60  
  Purchase #6 $12.73   8.600%   $13.8248   $13.82   $13.80   $13.80  
  Purchase #7 $191.39   10.853%   $212.1616   $212.16   $212.15   $212.20  
  7 purchase totals = $979.01       $1,068.5801   $1,068.56   $1,068.50   $1,068.60