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 $210.85   9.757%   $231.4226   $231.42   $231.40   $231.40  
  Purchase #2 $221.93   6.294%   $235.8983   $235.90   $235.90   $235.90  
  Purchase #3 $13.30   6.762%   $14.1993   $14.20   $14.20   $14.20  
  Purchase #4 $45.26   5.140%   $47.5864   $47.59   $47.60   $47.60  
  Purchase #5 $234.94   9.316%   $256.827   $256.83   $256.85   $256.80  
  Purchase #6 $167.92   9.273%   $183.4912   $183.49   $183.50   $183.50  
  Purchase #7 $178.92   3.245%   $184.726   $184.73   $184.75   $184.70  
  7 purchase totals = $1,073.12       $1,154.1508   $1,154.16   $1,154.20   $1,154.10