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 $69.93   7.294%   $75.0307   $75.03   $75.05   $75.00  
  Purchase #2 $163.82   11.209%   $182.1826   $182.18   $182.20   $182.20  
  Purchase #3 $118.87   11.580%   $132.6351   $132.64   $132.65   $132.60  
  Purchase #4 $217.46   6.432%   $231.447   $231.45   $231.45   $231.40  
  Purchase #5 $223.46   5.764%   $236.3402   $236.34   $236.35   $236.30  
  Purchase #6 $238.63   4.609%   $249.6285   $249.63   $249.65   $249.60  
  Purchase #7 $226.96   12.331%   $254.9464   $254.95   $254.95   $254.90  
  7 purchase totals = $1,259.13       $1,362.2105   $1,362.22   $1,362.30   $1,362.00