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	$111.41	11.447%	$124.1631	$124.16	$124.15	$124.20
Purchase #2	$143.81	5.435%	$151.6261	$151.63	$151.65	$151.60
Purchase #3	$91.66	13.354%	$103.9003	$103.90	$103.90	$103.90
Purchase #4	$164.84	5.584%	$174.0447	$174.04	$174.05	$174.00
Purchase #5	$98.59	12.860%	$111.2687	$111.27	$111.25	$111.30
Purchase #6	$17.66	10.494%	$19.5132	$19.51	$19.50	$19.50
Purchase #7	$107.32	3.579%	$111.161	$111.16	$111.15	$111.20
7 purchase totals =	$735.29		$795.6771	$795.67	$795.65	$795.70