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 $34.25   5.363%   $36.0868   $36.09   $36.10   $36.10  
  Purchase #2 $215.41   5.274%   $226.7707   $226.77   $226.75   $226.80  
  Purchase #3 $94.27   10.123%   $103.813   $103.81   $103.80   $103.80  
  Purchase #4 $250.43   4.332%   $261.2786   $261.28   $261.30   $261.30  
  Purchase #5 $210.94   3.814%   $218.9853   $218.99   $219.00   $219.00  
  Purchase #6 $188.90   6.489%   $201.1577   $201.16   $201.15   $201.20  
  Purchase #7 $219.27   6.396%   $233.2945   $233.29   $233.30   $233.30  
  7 purchase totals = $1,213.47       $1,281.3866   $1,281.39   $1,281.40   $1,281.50