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 $67.59   8.759%   $73.5102   $73.51   $73.50   $73.50  
  Purchase #2 $234.73   10.573%   $259.548   $259.55   $259.55   $259.50  
  Purchase #3 $143.42   12.165%   $160.867   $160.87   $160.85   $160.90  
  Purchase #4 $163.70   7.395%   $175.8056   $175.81   $175.80   $175.80  
  Purchase #5 $167.76   10.841%   $185.9469   $185.95   $185.95   $185.90  
  Purchase #6 $135.81   6.730%   $144.95   $144.95   $144.95   $145.00  
  Purchase #7 $134.33   9.255%   $146.7622   $146.76   $146.75   $146.80  
  7 purchase totals = $1,047.34       $1,147.3899   $1,147.40   $1,147.35   $1,147.40