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 $41.27   13.274%   $46.7482   $46.75   $46.75   $46.70  
  Purchase #2 $119.76   12.462%   $134.6845   $134.68   $134.70   $134.70  
  Purchase #3 $152.42   12.245%   $171.0838   $171.08   $171.10   $171.10  
  Purchase #4 $99.36   11.438%   $110.7248   $110.72   $110.70   $110.70  
  Purchase #5 $219.71   7.829%   $236.9111   $236.91   $236.90   $236.90  
  Purchase #6 $95.99   10.679%   $106.2408   $106.24   $106.25   $106.20  
  Purchase #7 $90.46   9.238%   $98.8167   $98.82   $98.80   $98.80  
  7 purchase totals = $818.97       $905.2099   $905.20   $905.20   $905.10