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 $182.26   7.832%   $196.5346   $196.53   $196.55   $196.50  
  Purchase #2 $244.67   4.451%   $255.5603   $255.56   $255.55   $255.60  
  Purchase #3 $209.82   7.871%   $226.3349   $226.33   $226.35   $226.30  
  Purchase #4 $232.96   5.704%   $246.248   $246.25   $246.25   $246.20  
  Purchase #5 $10.76   13.130%   $12.1728   $12.17   $12.15   $12.20  
  Purchase #6 $241.61   6.685%   $257.7616   $257.76   $257.75   $257.80  
  Purchase #7 $149.27   4.716%   $156.3096   $156.31   $156.30   $156.30  
  7 purchase totals = $1,271.35       $1,350.9218   $1,350.91   $1,350.90   $1,350.90