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	$208.78	9.451%	$228.5118	$228.51	$228.50	$228.50
Purchase #2	$30.29	9.467%	$33.1576	$33.16	$33.15	$33.20
Purchase #3	$88.81	10.276%	$97.9361	$97.94	$97.95	$97.90
Purchase #4	$120.74	5.604%	$127.5063	$127.51	$127.50	$127.50
Purchase #5	$19.46	4.309%	$20.2985	$20.30	$20.30	$20.30
Purchase #6	$125.38	13.501%	$142.3076	$142.31	$142.30	$142.30
Purchase #7	$217.50	12.227%	$244.0937	$244.09	$244.10	$244.10
7 purchase totals =	$810.96		$893.8116	$893.82	$893.80	$893.80