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 $184.41   11.691%   $205.9694   $205.97   $205.95   $206.00  
  Purchase #2 $189.79   3.804%   $197.0096   $197.01   $197.00   $197.00  
  Purchase #3 $40.63   5.840%   $43.0028   $43.00   $43.00   $43.00  
  Purchase #4 $245.53   7.298%   $263.4488   $263.45   $263.45   $263.40  
  Purchase #5 $232.28   12.431%   $261.1547   $261.15   $261.15   $261.20  
  Purchase #6 $25.93   12.753%   $29.2369   $29.24   $29.25   $29.20  
  Purchase #7 $88.90   8.131%   $96.1285   $96.13   $96.15   $96.10  
  7 purchase totals = $1,007.47       $1,095.9507   $1,095.95   $1,095.95   $1,095.90