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 $88.64   8.358%   $96.0485   $96.05   $96.05   $96.00  
  Purchase #2 $197.39   7.784%   $212.7548   $212.75   $212.75   $212.80  
  Purchase #3 $90.42   8.371%   $97.9891   $97.99   $98.00   $98.00  
  Purchase #4 $85.90   7.265%   $92.1406   $92.14   $92.15   $92.10  
  Purchase #5 $238.27   13.363%   $270.11   $270.11   $270.10   $270.10  
  Purchase #6 $113.33   5.222%   $119.2481   $119.25   $119.25   $119.20  
  Purchase #7 $9.29   12.416%   $10.4434   $10.44   $10.45   $10.40  
  7 purchase totals = $823.24       $898.7345   $898.73   $898.75   $898.60