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 $69.85   8.850%   $76.0317   $76.03   $76.05   $76.00  
  Purchase #2 $166.65   3.251%   $172.0678   $172.07   $172.05   $172.10  
  Purchase #3 $67.50   11.112%   $75.0006   $75.00   $75.00   $75.00  
  Purchase #4 $158.40   4.753%   $165.9288   $165.93   $165.95   $165.90  
  Purchase #5 $239.31   4.438%   $249.9306   $249.93   $249.95   $249.90  
  Purchase #6 $182.55   3.673%   $189.2551   $189.26   $189.25   $189.30  
  Purchase #7 $69.28   10.799%   $76.7615   $76.76   $76.75   $76.80  
  7 purchase totals = $953.54       $1,004.9761   $1,004.98   $1,005.00   $1,005.00