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 $59.60   4.726%   $62.4167   $62.42   $62.40   $62.40  
  Purchase #2 $219.25   10.211%   $241.6376   $241.64   $241.65   $241.60  
  Purchase #3 $176.67   11.615%   $197.1902   $197.19   $197.20   $197.20  
  Purchase #4 $124.93   5.704%   $132.056   $132.06   $132.05   $132.10  
  Purchase #5 $199.74   3.402%   $206.5352   $206.54   $206.55   $206.50  
  Purchase #6 $95.86   4.384%   $100.0625   $100.06   $100.05   $100.10  
  Purchase #7 $247.42   13.126%   $279.8963   $279.90   $279.90   $279.90  
  7 purchase totals = $1,123.47       $1,219.7945   $1,219.81   $1,219.80   $1,219.80