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 $57.71   8.269%   $62.482   $62.48   $62.50   $62.50  
  Purchase #2 $196.48   6.202%   $208.6657   $208.67   $208.65   $208.70  
  Purchase #3 $63.79   6.387%   $67.8643   $67.86   $67.85   $67.90  
  Purchase #4 $99.44   13.572%   $112.936   $112.94   $112.95   $112.90  
  Purchase #5 $205.87   8.828%   $224.0442   $224.04   $224.05   $224.00  
  Purchase #6 $79.66   4.361%   $83.134   $83.13   $83.15   $83.10  
  Purchase #7 $84.37   3.240%   $87.1036   $87.10   $87.10   $87.10  
  7 purchase totals = $787.32       $846.2298   $846.22   $846.25   $846.20