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 $106.87   9.440%   $116.9585   $116.96   $116.95   $117.00  
  Purchase #2 $180.31   8.758%   $196.1015   $196.10   $196.10   $196.10  
  Purchase #3 $221.66   3.538%   $229.5023   $229.50   $229.50   $229.50  
  Purchase #4 $235.45   4.694%   $246.502   $246.50   $246.50   $246.50  
  Purchase #5 $227.98   10.185%   $251.1998   $251.20   $251.20   $251.20  
  Purchase #6 $152.63   11.811%   $170.6571   $170.66   $170.65   $170.70  
  Purchase #7 $208.90   7.679%   $224.9414   $224.94   $224.95   $224.90  
  7 purchase totals = $1,333.80       $1,435.8626   $1,435.86   $1,435.85   $1,435.90