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	$51.33	4.112%	$53.4407	$53.44	$53.45	$53.40
Purchase #2	$78.69	13.387%	$89.2242	$89.22	$89.20	$89.20
Purchase #3	$84.75	7.632%	$91.2181	$91.22	$91.20	$91.20
Purchase #4	$173.61	12.659%	$195.5873	$195.59	$195.60	$195.60
Purchase #5	$117.58	8.378%	$127.4309	$127.43	$127.45	$127.40
Purchase #6	$69.83	7.276%	$74.9108	$74.91	$74.90	$74.90
Purchase #7	$116.34	12.324%	$130.6777	$130.68	$130.70	$130.70
7 purchase totals =	$692.13		$762.4897	$762.49	$762.50	$762.40