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 $61.36   9.619%   $67.2622   $67.26   $67.25   $67.30  
  Purchase #2 $142.64   13.370%   $161.711   $161.71   $161.70   $161.70  
  Purchase #3 $238.57   5.608%   $251.949   $251.95   $251.95   $251.90  
  Purchase #4 $55.90   12.230%   $62.7366   $62.74   $62.75   $62.70  
  Purchase #5 $121.35   4.612%   $126.9467   $126.95   $126.95   $126.90  
  Purchase #6 $248.45   11.118%   $276.0727   $276.07   $276.05   $276.10  
  Purchase #7 $95.47   7.807%   $102.9233   $102.92   $102.90   $102.90  
  7 purchase totals = $963.74       $1,049.6015   $1,049.60   $1,049.55   $1,049.50