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 $236.41   10.800%   $261.9423   $261.94   $261.95   $261.90  
  Purchase #2 $118.82   6.427%   $126.4566   $126.46   $126.45   $126.50  
  Purchase #3 $83.95   7.439%   $90.195   $90.20   $90.20   $90.20  
  Purchase #4 $149.49   10.512%   $165.2044   $165.20   $165.20   $165.20  
  Purchase #5 $219.27   3.657%   $227.2887   $227.29   $227.30   $227.30  
  Purchase #6 $28.44   7.160%   $30.4763   $30.48   $30.50   $30.50  
  Purchase #7 $241.46   8.668%   $262.3898   $262.39   $262.40   $262.40  
  7 purchase totals = $1,077.84       $1,163.9531   $1,163.96   $1,164.00   $1,164.00