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 $55.79   11.384%   $62.1411   $62.14   $62.15   $62.10  
  Purchase #2 $96.29   6.521%   $102.5691   $102.57   $102.55   $102.60  
  Purchase #3 $195.44   6.514%   $208.171   $208.17   $208.15   $208.20  
  Purchase #4 $118.47   6.229%   $125.8495   $125.85   $125.85   $125.80  
  Purchase #5 $222.40   3.147%   $229.3989   $229.40   $229.40   $229.40  
  Purchase #6 $244.41   9.161%   $266.8004   $266.80   $266.80   $266.80  
  Purchase #7 $226.64   13.764%   $257.8347   $257.83   $257.85   $257.80  
  7 purchase totals = $1,159.44       $1,252.7647   $1,252.76   $1,252.75   $1,252.70