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 $246.99   6.132%   $262.1354   $262.14   $262.15   $262.10  
  Purchase #2 $67.75   13.405%   $76.8319   $76.83   $76.85   $76.80  
  Purchase #3 $148.71   5.697%   $157.182   $157.18   $157.20   $157.20  
  Purchase #4 $140.86   7.239%   $151.0569   $151.06   $151.05   $151.10  
  Purchase #5 $119.86   11.445%   $133.578   $133.58   $133.60   $133.60  
  Purchase #6 $246.28   6.522%   $262.3424   $262.34   $262.35   $262.30  
  Purchase #7 $71.73   12.634%   $80.7924   $80.79   $80.80   $80.80  
  7 purchase totals = $1,042.18       $1,123.9190   $1,123.92   $1,124.00   $1,123.90