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 $215.71   10.872%   $239.162   $239.16   $239.15   $239.20  
  Purchase #2 $101.34   10.775%   $112.2594   $112.26   $112.25   $112.30  
  Purchase #3 $175.67   9.738%   $192.7767   $192.78   $192.80   $192.80  
  Purchase #4 $148.43   13.144%   $167.9396   $167.94   $167.95   $167.90  
  Purchase #5 $143.38   9.169%   $156.5265   $156.53   $156.55   $156.50  
  Purchase #6 $226.57   3.702%   $234.9576   $234.96   $234.95   $235.00  
  Purchase #7 $93.29   4.325%   $97.3248   $97.32   $97.30   $97.30  
  7 purchase totals = $1,104.39       $1,200.9466   $1,200.95   $1,200.95   $1,201.00