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	$226.85	7.686%	$244.2857	$244.29	$244.30	$244.30
Purchase #2	$49.43	3.504%	$51.162	$51.16	$51.15	$51.20
Purchase #3	$135.37	13.597%	$153.7763	$153.78	$153.80	$153.80
Purchase #4	$139.32	10.753%	$154.3011	$154.30	$154.30	$154.30
Purchase #5	$191.94	13.268%	$217.4066	$217.41	$217.40	$217.40
Purchase #6	$54.71	12.195%	$61.3819	$61.38	$61.40	$61.40
Purchase #7	$87.47	13.322%	$99.1228	$99.12	$99.10	$99.10
7 purchase totals =	$885.09		$981.4364	$981.44	$981.45	$981.50