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 $196.85   8.561%   $213.7023   $213.70   $213.70   $213.70  
  Purchase #2 $14.57   7.688%   $15.6901   $15.69   $15.70   $15.70  
  Purchase #3 $216.68   9.376%   $236.9959   $237.00   $237.00   $237.00  
  Purchase #4 $132.37   10.537%   $146.3178   $146.32   $146.30   $146.30  
  Purchase #5 $66.91   3.187%   $69.0424   $69.04   $69.05   $69.00  
  Purchase #6 $95.73   11.359%   $106.604   $106.60   $106.60   $106.60  
  Purchase #7 $239.46   9.678%   $262.6349   $262.63   $262.65   $262.60  
  7 purchase totals = $962.57       $1,050.9874   $1,050.98   $1,051.00   $1,050.90