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 $119.30   6.281%   $126.7932   $126.79   $126.80   $126.80  
  Purchase #2 $217.81   12.346%   $244.7008   $244.70   $244.70   $244.70  
  Purchase #3 $58.80   8.373%   $63.7233   $63.72   $63.70   $63.70  
  Purchase #4 $140.30   8.757%   $152.5861   $152.59   $152.60   $152.60  
  Purchase #5 $178.95   10.467%   $197.6807   $197.68   $197.70   $197.70  
  Purchase #6 $201.44   4.190%   $209.8803   $209.88   $209.90   $209.90  
  Purchase #7 $114.97   12.379%   $129.2021   $129.20   $129.20   $129.20  
  7 purchase totals = $1,031.57       $1,124.5665   $1,124.56   $1,124.60   $1,124.60