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	$92.89	3.494%	$96.1356	$96.14	$96.15	$96.10
Purchase #2	$53.46	9.515%	$58.5467	$58.55	$58.55	$58.50
Purchase #3	$123.32	6.636%	$131.5035	$131.50	$131.50	$131.50
Purchase #4	$160.37	8.249%	$173.5989	$173.60	$173.60	$173.60
Purchase #5	$177.74	6.632%	$189.5277	$189.53	$189.55	$189.50
Purchase #6	$229.35	9.708%	$251.6153	$251.62	$251.60	$251.60
Purchase #7	$74.29	4.727%	$77.8017	$77.80	$77.80	$77.80
7 purchase totals =	$911.42		$978.7294	$978.74	$978.75	$978.60