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 $188.93   3.356%   $195.2705   $195.27   $195.25   $195.30  
  Purchase #2 $233.94   12.194%   $262.4666   $262.47   $262.45   $262.50  
  Purchase #3 $96.34   4.557%   $100.7302   $100.73   $100.75   $100.70  
  Purchase #4 $221.81   4.413%   $231.5985   $231.60   $231.60   $231.60  
  Purchase #5 $187.92   5.592%   $198.4285   $198.43   $198.45   $198.40  
  Purchase #6 $106.67   13.466%   $121.0342   $121.03   $121.05   $121.00  
  Purchase #7 $164.73   13.645%   $187.2074   $187.21   $187.20   $187.20  
  7 purchase totals = $1,200.34       $1,296.7359   $1,296.74   $1,296.75   $1,296.70