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	$219.42	8.317%	$237.6692	$237.67	$237.65	$237.70
Purchase #2	$97.70	6.298%	$103.8531	$103.85	$103.85	$103.90
Purchase #3	$32.85	11.142%	$36.5101	$36.51	$36.50	$36.50
Purchase #4	$57.30	6.757%	$61.1718	$61.17	$61.15	$61.20
Purchase #5	$155.74	11.547%	$173.7233	$173.72	$173.70	$173.70
Purchase #6	$56.89	10.483%	$62.8538	$62.85	$62.85	$62.90
Purchase #7	$19.49	9.362%	$21.3147	$21.31	$21.30	$21.30
7 purchase totals =	$639.39		$697.0960	$697.08	$697.00	$697.20