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	$49.69	5.699%	$52.5218	$52.52	$52.50	$52.50
Purchase #2	$91.60	6.383%	$97.4468	$97.45	$97.45	$97.40
Purchase #3	$40.86	4.325%	$42.6272	$42.63	$42.65	$42.60
Purchase #4	$109.91	7.170%	$117.7905	$117.79	$117.80	$117.80
Purchase #5	$140.25	4.607%	$146.7113	$146.71	$146.70	$146.70
Purchase #6	$156.38	7.519%	$168.1382	$168.14	$168.15	$168.10
Purchase #7	$107.64	3.590%	$111.5043	$111.50	$111.50	$111.50
7 purchase totals =	$696.33		$736.7401	$736.74	$736.75	$736.60