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 $61.91   9.122%   $67.5574   $67.56   $67.55   $67.60  
  Purchase #2 $235.50   5.707%   $248.94   $248.94   $248.95   $248.90  
  Purchase #3 $44.94   9.382%   $49.1563   $49.16   $49.15   $49.20  
  Purchase #4 $8.74   5.216%   $9.1959   $9.20   $9.20   $9.20  
  Purchase #5 $214.80   6.797%   $229.4   $229.40   $229.40   $229.40  
  Purchase #6 $213.79   12.831%   $241.2214   $241.22   $241.20   $241.20  
  Purchase #7 $69.63   3.521%   $72.0817   $72.08   $72.10   $72.10  
  7 purchase totals = $849.31       $917.5527   $917.56   $917.55   $917.60