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	$200.60	9.695%	$220.0482	$220.05	$220.05	$220.00
Purchase #2	$122.47	7.404%	$131.5377	$131.54	$131.55	$131.50
Purchase #3	$205.33	11.707%	$229.368	$229.37	$229.35	$229.40
Purchase #4	$152.89	13.717%	$173.8619	$173.86	$173.85	$173.90
Purchase #5	$151.49	4.676%	$158.5737	$158.57	$158.55	$158.60
Purchase #6	$149.25	6.431%	$158.8483	$158.85	$158.85	$158.80
Purchase #7	$112.82	3.328%	$116.5746	$116.57	$116.55	$116.60
7 purchase totals =	$1,094.85		$1,188.8124	$1,188.81	$1,188.75	$1,188.80