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 $59.81   5.756%   $63.2527   $63.25   $63.25   $63.30  
  Purchase #2 $250.61   11.437%   $279.2723   $279.27   $279.25   $279.30  
  Purchase #3 $145.27   8.621%   $157.7937   $157.79   $157.80   $157.80  
  Purchase #4 $213.97   11.400%   $238.3626   $238.36   $238.35   $238.40  
  Purchase #5 $101.69   8.603%   $110.4384   $110.44   $110.45   $110.40  
  Purchase #6 $186.97   9.853%   $205.3922   $205.39   $205.40   $205.40  
  Purchase #7 $105.45   12.652%   $118.7915   $118.79   $118.80   $118.80  
  7 purchase totals = $1,063.77       $1,173.3034   $1,173.29   $1,173.30   $1,173.40