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	$198.71	5.274%	$209.19	$209.19	$209.20	$209.20
Purchase #2	$205.38	12.825%	$231.72	$231.72	$231.70	$231.70
Purchase #3	$196.38	9.705%	$215.4387	$215.44	$215.45	$215.40
Purchase #4	$110.43	12.177%	$123.8771	$123.88	$123.90	$123.90
Purchase #5	$231.80	4.349%	$241.881	$241.88	$241.90	$241.90
Purchase #6	$171.53	3.572%	$177.6571	$177.66	$177.65	$177.70
Purchase #7	$80.62	12.458%	$90.6636	$90.66	$90.65	$90.70
7 purchase totals =	$1,194.85		$1,290.4275	$1,290.43	$1,290.45	$1,290.50