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 $59.55   4.433%   $62.1899   $62.19   $62.20   $62.20  
  Purchase #2 $244.88   8.678%   $266.1307   $266.13   $266.15   $266.10  
  Purchase #3 $241.86   13.272%   $273.9597   $273.96   $273.95   $274.00  
  Purchase #4 $70.68   10.392%   $78.0251   $78.03   $78.05   $78.00  
  Purchase #5 $194.35   11.352%   $216.4126   $216.41   $216.40   $216.40  
  Purchase #6 $117.97   7.482%   $126.7965   $126.80   $126.80   $126.80  
  Purchase #7 $119.93   4.273%   $125.0546   $125.05   $125.05   $125.10  
  7 purchase totals = $1,049.22       $1,148.5691   $1,148.57   $1,148.60   $1,148.60