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 $173.55   13.501%   $196.981   $196.98   $197.00   $197.00  
  Purchase #2 $209.86   9.357%   $229.4966   $229.50   $229.50   $229.50  
  Purchase #3 $69.43   10.823%   $76.9444   $76.94   $76.95   $76.90  
  Purchase #4 $49.64   4.254%   $51.7517   $51.75   $51.75   $51.80  
  Purchase #5 $6.26   5.833%   $6.6251   $6.63   $6.65   $6.60  
  Purchase #6 $113.27   13.399%   $128.447   $128.45   $128.45   $128.40  
  Purchase #7 $250.26   7.645%   $269.3924   $269.39   $269.40   $269.40  
  7 purchase totals = $872.27       $959.6382   $959.64   $959.70   $959.60