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 $119.85   5.293%   $126.1937   $126.19   $126.20   $126.20  
  Purchase #2 $137.49   12.186%   $154.2445   $154.24   $154.25   $154.20  
  Purchase #3 $210.40   10.516%   $232.5257   $232.53   $232.55   $232.50  
  Purchase #4 $248.26   7.721%   $267.4282   $267.43   $267.45   $267.40  
  Purchase #5 $244.88   3.345%   $253.0712   $253.07   $253.05   $253.10  
  Purchase #6 $57.31   3.655%   $59.4047   $59.40   $59.40   $59.40  
  Purchase #7 $24.97   5.302%   $26.2939   $26.29   $26.30   $26.30  
  7 purchase totals = $1,043.16       $1,119.1619   $1,119.15   $1,119.20   $1,119.10