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 $60.85   5.668%   $64.299   $64.30   $64.30   $64.30  
  Purchase #2 $248.34   5.326%   $261.5666   $261.57   $261.55   $261.60  
  Purchase #3 $207.53   7.548%   $223.1944   $223.19   $223.20   $223.20  
  Purchase #4 $143.68   12.312%   $161.3699   $161.37   $161.35   $161.40  
  Purchase #5 $125.97   6.571%   $134.2475   $134.25   $134.25   $134.20  
  Purchase #6 $6.71   4.691%   $7.0248   $7.02   $7.00   $7.00  
  Purchase #7 $192.72   9.165%   $210.3828   $210.38   $210.40   $210.40  
  7 purchase totals = $985.80       $1,062.0850   $1,062.08   $1,062.05   $1,062.10