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 $86.95   10.708%   $96.2606   $96.26   $96.25   $96.30  
  Purchase #2 $182.39   10.532%   $201.5993   $201.60   $201.60   $201.60  
  Purchase #3 $203.80   11.621%   $227.4836   $227.48   $227.50   $227.50  
  Purchase #4 $136.34   12.232%   $153.0171   $153.02   $153.00   $153.00  
  Purchase #5 $42.83   11.212%   $47.6321   $47.63   $47.65   $47.60  
  Purchase #6 $136.63   8.618%   $148.4048   $148.40   $148.40   $148.40  
  Purchase #7 $230.82   9.567%   $252.9025   $252.90   $252.90   $252.90  
  7 purchase totals = $1,019.76       $1,127.3000   $1,127.29   $1,127.30   $1,127.30