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 $41.32   8.784%   $44.9495   $44.95   $44.95   $44.90  
  Purchase #2 $236.77   10.766%   $262.2607   $262.26   $262.25   $262.30  
  Purchase #3 $19.55   8.429%   $21.1979   $21.20   $21.20   $21.20  
  Purchase #4 $128.97   7.484%   $138.6221   $138.62   $138.60   $138.60  
  Purchase #5 $231.67   10.300%   $255.532   $255.53   $255.55   $255.50  
  Purchase #6 $247.77   3.782%   $257.1407   $257.14   $257.15   $257.10  
  Purchase #7 $213.60   5.866%   $226.1298   $226.13   $226.15   $226.10  
  7 purchase totals = $1,119.65       $1,205.8327   $1,205.83   $1,205.85   $1,205.70