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 $114.63   4.380%   $119.6508   $119.65   $119.65   $119.70  
  Purchase #2 $205.86   3.760%   $213.6003   $213.60   $213.60   $213.60  
  Purchase #3 $37.34   13.511%   $42.385   $42.39   $42.40   $42.40  
  Purchase #4 $188.76   12.114%   $211.6264   $211.63   $211.65   $211.60  
  Purchase #5 $245.77   11.810%   $274.7954   $274.80   $274.80   $274.80  
  Purchase #6 $192.87   6.864%   $206.1086   $206.11   $206.10   $206.10  
  Purchase #7 $240.50   6.159%   $255.3124   $255.31   $255.30   $255.30  
  7 purchase totals = $1,225.73       $1,323.4789   $1,323.49   $1,323.50   $1,323.50