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 $58.39   7.784%   $62.9351   $62.94   $62.95   $62.90  
  Purchase #2 $64.92   13.473%   $73.6667   $73.67   $73.65   $73.70  
  Purchase #3 $82.80   7.554%   $89.0547   $89.05   $89.05   $89.10  
  Purchase #4 $39.47   10.194%   $43.4936   $43.49   $43.50   $43.50  
  Purchase #5 $76.96   5.617%   $81.2828   $81.28   $81.30   $81.30  
  Purchase #6 $168.57   4.398%   $175.9837   $175.98   $176.00   $176.00  
  Purchase #7 $197.33   4.507%   $206.2237   $206.22   $206.20   $206.20  
  7 purchase totals = $688.44       $732.6403   $732.63   $732.65   $732.70