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 $118.44   6.187%   $125.7679   $125.77   $125.75   $125.80  
  Purchase #2 $42.79   10.592%   $47.3223   $47.32   $47.30   $47.30  
  Purchase #3 $69.91   5.571%   $73.8047   $73.80   $73.80   $73.80  
  Purchase #4 $161.38   9.848%   $177.2727   $177.27   $177.25   $177.30  
  Purchase #5 $84.52   3.378%   $87.3751   $87.38   $87.40   $87.40  
  Purchase #6 $229.54   6.540%   $244.5519   $244.55   $244.55   $244.60  
  Purchase #7 $153.28   11.616%   $171.085   $171.09   $171.10   $171.10  
  7 purchase totals = $859.86       $927.1796   $927.18   $927.15   $927.30