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	$19.73	13.792%	$22.4512	$22.45	$22.45	$22.50
Purchase #2	$244.77	4.499%	$255.7822	$255.78	$255.80	$255.80
Purchase #3	$222.46	11.505%	$248.054	$248.05	$248.05	$248.10
Purchase #4	$91.62	12.460%	$103.0359	$103.04	$103.05	$103.00
Purchase #5	$91.58	13.323%	$103.7812	$103.78	$103.80	$103.80
Purchase #6	$197.30	9.115%	$215.2839	$215.28	$215.30	$215.30
Purchase #7	$84.57	7.681%	$91.0658	$91.07	$91.05	$91.10
7 purchase totals =	$952.03		$1,039.4542	$1,039.45	$1,039.50	$1,039.60