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 $118.61   4.561%   $124.0198   $124.02   $124.00   $124.00  
  Purchase #2 $108.99   11.213%   $121.211   $121.21   $121.20   $121.20  
  Purchase #3 $69.74   6.193%   $74.059   $74.06   $74.05   $74.10  
  Purchase #4 $15.78   11.102%   $17.5319   $17.53   $17.55   $17.50  
  Purchase #5 $67.64   8.249%   $73.2196   $73.22   $73.20   $73.20  
  Purchase #6 $159.73   5.338%   $168.2564   $168.26   $168.25   $168.30  
  Purchase #7 $200.42   3.162%   $206.7573   $206.76   $206.75   $206.80  
  7 purchase totals = $740.91       $785.0550   $785.06   $785.00   $785.10