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 $201.26   3.872%   $209.0528   $209.05   $209.05   $209.10  
  Purchase #2 $62.87   9.758%   $69.0049   $69.00   $69.00   $69.00  
  Purchase #3 $84.55   12.317%   $94.964   $94.96   $94.95   $95.00  
  Purchase #4 $178.92   7.568%   $192.4607   $192.46   $192.45   $192.50  
  Purchase #5 $119.95   13.304%   $135.9081   $135.91   $135.90   $135.90  
  Purchase #6 $29.85   10.609%   $33.0168   $33.02   $33.00   $33.00  
  Purchase #7 $70.69   3.823%   $73.3925   $73.39   $73.40   $73.40  
  7 purchase totals = $748.09       $807.7998   $807.79   $807.75   $807.90