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 $207.56   12.664%   $233.8454   $233.85   $233.85   $233.80  
  Purchase #2 $164.47   5.353%   $173.2741   $173.27   $173.25   $173.30  
  Purchase #3 $80.71   4.781%   $84.5687   $84.57   $84.55   $84.60  
  Purchase #4 $191.58   7.489%   $205.9274   $205.93   $205.95   $205.90  
  Purchase #5 $194.77   6.621%   $207.6657   $207.67   $207.65   $207.70  
  Purchase #6 $170.61   7.564%   $183.5149   $183.51   $183.50   $183.50  
  Purchase #7 $14.34   10.654%   $15.8678   $15.87   $15.85   $15.90  
  7 purchase totals = $1,024.04       $1,104.6640   $1,104.67   $1,104.60   $1,104.70