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 $43.94   9.741%   $48.2202   $48.22   $48.20   $48.20  
  Purchase #2 $227.41   9.362%   $248.7001   $248.70   $248.70   $248.70  
  Purchase #3 $229.99   12.132%   $257.8924   $257.89   $257.90   $257.90  
  Purchase #4 $115.65   12.681%   $130.3156   $130.32   $130.30   $130.30  
  Purchase #5 $93.65   10.525%   $103.5067   $103.51   $103.50   $103.50  
  Purchase #6 $230.60   12.529%   $259.4919   $259.49   $259.50   $259.50  
  Purchase #7 $244.42   13.339%   $277.0232   $277.02   $277.00   $277.00  
  7 purchase totals = $1,185.66       $1,325.1501   $1,325.15   $1,325.10   $1,325.10