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 $34.66   7.401%   $37.2252   $37.23   $37.25   $37.20  
  Purchase #2 $112.71   12.651%   $126.9689   $126.97   $126.95   $127.00  
  Purchase #3 $164.64   3.487%   $170.381   $170.38   $170.40   $170.40  
  Purchase #4 $204.25   5.387%   $215.2529   $215.25   $215.25   $215.30  
  Purchase #5 $128.29   8.636%   $139.3691   $139.37   $139.35   $139.40  
  Purchase #6 $245.60   3.764%   $254.8444   $254.84   $254.85   $254.80  
  Purchase #7 $64.88   8.460%   $70.3688   $70.37   $70.35   $70.40  
  7 purchase totals = $955.03       $1,014.4103   $1,014.41   $1,014.40   $1,014.50