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 $83.98   12.579%   $94.5438   $94.54   $94.55   $94.50  
  Purchase #2 $167.83   8.559%   $182.1946   $182.19   $182.20   $182.20  
  Purchase #3 $84.26   12.804%   $95.0487   $95.05   $95.05   $95.00  
  Purchase #4 $200.90   13.387%   $227.7945   $227.79   $227.80   $227.80  
  Purchase #5 $145.56   10.640%   $161.0476   $161.05   $161.05   $161.00  
  Purchase #6 $146.51   3.808%   $152.0891   $152.09   $152.10   $152.10  
  Purchase #7 $100.36   9.474%   $109.8681   $109.87   $109.85   $109.90  
  7 purchase totals = $929.40       $1,022.5864   $1,022.58   $1,022.60   $1,022.50