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	$160.33	5.172%	$168.6223	$168.62	$168.60	$168.60
Purchase #2	$134.41	3.391%	$138.9678	$138.97	$138.95	$139.00
Purchase #3	$81.46	12.247%	$91.4364	$91.44	$91.45	$91.40
Purchase #4	$155.65	13.612%	$176.8371	$176.84	$176.85	$176.80
Purchase #5	$223.78	12.826%	$252.482	$252.48	$252.50	$252.50
Purchase #6	$232.89	9.625%	$255.3057	$255.31	$255.30	$255.30
Purchase #7	$36.37	11.668%	$40.6137	$40.61	$40.60	$40.60
7 purchase totals =	$1,024.89		$1,124.2650	$1,124.27	$1,124.25	$1,124.20