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 $82.61   12.107%   $92.6116   $92.61   $92.60   $92.60  
  Purchase #2 $17.55   11.808%   $19.6223   $19.62   $19.60   $19.60  
  Purchase #3 $231.51   4.626%   $242.2197   $242.22   $242.20   $242.20  
  Purchase #4 $51.37   13.195%   $58.1483   $58.15   $58.15   $58.10  
  Purchase #5 $195.64   11.255%   $217.6593   $217.66   $217.65   $217.70  
  Purchase #6 $170.47   9.183%   $186.1243   $186.12   $186.10   $186.10  
  Purchase #7 $219.95   11.155%   $244.4854   $244.49   $244.50   $244.50  
  7 purchase totals = $969.10       $1,060.8709   $1,060.87   $1,060.80   $1,060.80