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	$146.42	3.763%	$151.9298	$151.93	$151.95	$151.90
Purchase #2	$201.46	13.281%	$228.2159	$228.22	$228.20	$228.20
Purchase #3	$224.27	3.415%	$231.9288	$231.93	$231.95	$231.90
Purchase #4	$127.59	10.579%	$141.0877	$141.09	$141.10	$141.10
Purchase #5	$155.27	11.777%	$173.5561	$173.56	$173.55	$173.60
Purchase #6	$76.68	9.103%	$83.6602	$83.66	$83.65	$83.70
Purchase #7	$154.94	10.837%	$171.7308	$171.73	$171.75	$171.70
7 purchase totals =	$1,086.63		$1,182.1093	$1,182.12	$1,182.15	$1,182.10