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 $61.69   12.687%   $69.5166   $69.52   $69.50   $69.50  
  Purchase #2 $195.95   6.327%   $208.3478   $208.35   $208.35   $208.30  
  Purchase #3 $52.98   10.846%   $58.7262   $58.73   $58.75   $58.70  
  Purchase #4 $118.79   10.783%   $131.5991   $131.60   $131.60   $131.60  
  Purchase #5 $163.34   11.590%   $182.2711   $182.27   $182.25   $182.30  
  Purchase #6 $107.94   10.426%   $119.1938   $119.19   $119.20   $119.20  
  Purchase #7 $17.97   7.554%   $19.3275   $19.33   $19.35   $19.30  
  7 purchase totals = $718.66       $788.9821   $788.99   $789.00   $788.90