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 $112.25   12.606%   $126.4002   $126.40   $126.40   $126.40  
  Purchase #2 $92.32   4.828%   $96.7772   $96.78   $96.80   $96.80  
  Purchase #3 $229.90   6.216%   $244.1906   $244.19   $244.20   $244.20  
  Purchase #4 $202.74   4.492%   $211.8471   $211.85   $211.85   $211.80  
  Purchase #5 $168.67   10.115%   $185.731   $185.73   $185.75   $185.70  
  Purchase #6 $212.97   13.706%   $242.1597   $242.16   $242.15   $242.20  
  Purchase #7 $134.44   10.307%   $148.2967   $148.30   $148.30   $148.30  
  7 purchase totals = $1,153.29       $1,255.4025   $1,255.41   $1,255.45   $1,255.40