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 $209.69   12.811%   $236.5534   $236.55   $236.55   $236.60  
  Purchase #2 $209.33   10.147%   $230.5707   $230.57   $230.55   $230.60  
  Purchase #3 $243.55   9.240%   $266.054   $266.05   $266.05   $266.10  
  Purchase #4 $203.49   4.570%   $212.7895   $212.79   $212.80   $212.80  
  Purchase #5 $196.68   10.262%   $216.8633   $216.86   $216.85   $216.90  
  Purchase #6 $106.76   4.559%   $111.6272   $111.63   $111.65   $111.60  
  Purchase #7 $207.73   6.756%   $221.7642   $221.76   $221.75   $221.80  
  7 purchase totals = $1,377.23       $1,496.2223   $1,496.21   $1,496.20   $1,496.40