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 $43.76   10.409%   $48.315   $48.32   $48.30   $48.30  
  Purchase #2 $168.33   8.696%   $182.968   $182.97   $182.95   $183.00  
  Purchase #3 $250.55   7.322%   $268.8953   $268.90   $268.90   $268.90  
  Purchase #4 $15.65   8.228%   $16.9377   $16.94   $16.95   $16.90  
  Purchase #5 $158.49   10.530%   $175.179   $175.18   $175.20   $175.20  
  Purchase #6 $205.30   5.196%   $215.9674   $215.97   $215.95   $216.00  
  Purchase #7 $56.89   7.488%   $61.1499   $61.15   $61.15   $61.10  
  7 purchase totals = $898.97       $969.4123   $969.43   $969.40   $969.40