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	$137.32	7.748%	$147.9596	$147.96	$147.95	$148.00
Purchase #2	$171.67	4.523%	$179.4346	$179.43	$179.45	$179.40
Purchase #3	$11.40	5.863%	$12.0684	$12.07	$12.05	$12.10
Purchase #4	$158.32	6.657%	$168.8594	$168.86	$168.85	$168.90
Purchase #5	$144.47	7.614%	$155.4699	$155.47	$155.45	$155.50
Purchase #6	$32.73	3.118%	$33.7505	$33.75	$33.75	$33.80
Purchase #7	$38.77	11.246%	$43.1301	$43.13	$43.15	$43.10
7 purchase totals =	$694.68		$740.6725	$740.67	$740.65	$740.80