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 $67.27   3.408%   $69.5626   $69.56   $69.55   $69.60  
  Purchase #2 $98.64   7.296%   $105.8368   $105.84   $105.85   $105.80  
  Purchase #3 $83.38   5.472%   $87.9426   $87.94   $87.95   $87.90  
  Purchase #4 $64.66   11.432%   $72.0519   $72.05   $72.05   $72.10  
  Purchase #5 $173.73   3.316%   $179.4909   $179.49   $179.50   $179.50  
  Purchase #6 $23.99   4.174%   $24.9913   $24.99   $25.00   $25.00  
  Purchase #7 $204.45   7.827%   $220.4523   $220.45   $220.45   $220.50  
  7 purchase totals = $716.12       $760.3284   $760.32   $760.35   $760.40