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 $58.69   3.411%   $60.6919   $60.69   $60.70   $60.70  
  Purchase #2 $193.41   12.267%   $217.1356   $217.14   $217.15   $217.10  
  Purchase #3 $113.30   7.274%   $121.5414   $121.54   $121.55   $121.50  
  Purchase #4 $243.38   13.152%   $275.3893   $275.39   $275.40   $275.40  
  Purchase #5 $127.36   7.510%   $136.9247   $136.92   $136.90   $136.90  
  Purchase #6 $192.66   6.216%   $204.6357   $204.64   $204.65   $204.60  
  Purchase #7 $81.44   7.857%   $87.8387   $87.84   $87.85   $87.80  
  7 purchase totals = $1,010.24       $1,104.1573   $1,104.16   $1,104.20   $1,104.00