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 $196.62   5.549%   $207.5304   $207.53   $207.55   $207.50  
  Purchase #2 $109.95   11.527%   $122.6239   $122.62   $122.60   $122.60  
  Purchase #3 $103.82   4.385%   $108.3725   $108.37   $108.35   $108.40  
  Purchase #4 $227.61   5.842%   $240.907   $240.91   $240.90   $240.90  
  Purchase #5 $60.38   4.565%   $63.1363   $63.14   $63.15   $63.10  
  Purchase #6 $12.70   7.511%   $13.6539   $13.65   $13.65   $13.70  
  Purchase #7 $10.27   9.725%   $11.2688   $11.27   $11.25   $11.30  
  7 purchase totals = $721.35       $767.4928   $767.49   $767.45   $767.50