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 $105.67   13.268%   $119.6903   $119.69   $119.70   $119.70  
  Purchase #2 $214.70   10.687%   $237.645   $237.65   $237.65   $237.60  
  Purchase #3 $128.27   3.440%   $132.6825   $132.68   $132.70   $132.70  
  Purchase #4 $122.92   9.166%   $134.1868   $134.19   $134.20   $134.20  
  Purchase #5 $24.50   7.530%   $26.3449   $26.34   $26.35   $26.30  
  Purchase #6 $62.34   3.226%   $64.3511   $64.35   $64.35   $64.40  
  Purchase #7 $173.87   5.105%   $182.7461   $182.75   $182.75   $182.70  
  7 purchase totals = $832.27       $897.6467   $897.65   $897.70   $897.60