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 $119.83   5.417%   $126.3212   $126.32   $126.30   $126.30  
  Purchase #2 $188.43   3.660%   $195.3265   $195.33   $195.35   $195.30  
  Purchase #3 $73.29   6.451%   $78.0179   $78.02   $78.00   $78.00  
  Purchase #4 $91.40   11.286%   $101.7154   $101.72   $101.70   $101.70  
  Purchase #5 $237.62   6.705%   $253.5524   $253.55   $253.55   $253.60  
  Purchase #6 $45.76   9.773%   $50.2321   $50.23   $50.25   $50.20  
  Purchase #7 $218.53   4.860%   $229.1506   $229.15   $229.15   $229.20  
  7 purchase totals = $974.86       $1,034.3161   $1,034.32   $1,034.30   $1,034.30