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 $31.61   13.413%   $35.8498   $35.85   $35.85   $35.80  
  Purchase #2 $183.74   8.846%   $199.9936   $199.99   $200.00   $200.00  
  Purchase #3 $88.86   8.253%   $96.1936   $96.19   $96.20   $96.20  
  Purchase #4 $29.57   12.676%   $33.3183   $33.32   $33.30   $33.30  
  Purchase #5 $101.82   7.549%   $109.5064   $109.51   $109.50   $109.50  
  Purchase #6 $115.27   5.143%   $121.1983   $121.20   $121.20   $121.20  
  Purchase #7 $123.26   11.129%   $136.9776   $136.98   $137.00   $137.00  
  7 purchase totals = $674.13       $733.0376   $733.04   $733.05   $733.00