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 $119.96   5.558%   $126.6274   $126.63   $126.65   $126.60  
  Purchase #2 $64.42   7.505%   $69.2547   $69.25   $69.25   $69.30  
  Purchase #3 $223.66   6.292%   $237.7327   $237.73   $237.75   $237.70  
  Purchase #4 $138.97   4.280%   $144.9179   $144.92   $144.90   $144.90  
  Purchase #5 $95.83   8.650%   $104.1193   $104.12   $104.10   $104.10  
  Purchase #6 $125.82   5.752%   $133.0572   $133.06   $133.05   $133.10  
  Purchase #7 $46.98   7.326%   $50.4218   $50.42   $50.40   $50.40  
  7 purchase totals = $815.64       $866.1310   $866.13   $866.10   $866.10