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 $212.75   10.587%   $235.2738   $235.27   $235.25   $235.30  
  Purchase #2 $221.94   6.642%   $236.6813   $236.68   $236.70   $236.70  
  Purchase #3 $231.86   9.307%   $253.4392   $253.44   $253.45   $253.40  
  Purchase #4 $236.45   6.803%   $252.5357   $252.54   $252.55   $252.50  
  Purchase #5 $32.25   12.569%   $36.3035   $36.30   $36.30   $36.30  
  Purchase #6 $190.36   10.816%   $210.9493   $210.95   $210.95   $210.90  
  Purchase #7 $163.99   3.842%   $170.2905   $170.29   $170.30   $170.30  
  7 purchase totals = $1,289.60       $1,395.4733   $1,395.47   $1,395.50   $1,395.40