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	$152.45	13.759%	$173.4256	$173.43	$173.45	$173.40
Purchase #2	$140.35	7.575%	$150.9815	$150.98	$151.00	$151.00
Purchase #3	$145.54	13.757%	$165.5619	$165.56	$165.55	$165.60
Purchase #4	$42.62	8.245%	$46.134	$46.13	$46.15	$46.10
Purchase #5	$117.48	12.402%	$132.0499	$132.05	$132.05	$132.00
Purchase #6	$172.59	4.126%	$179.7111	$179.71	$179.70	$179.70
Purchase #7	$33.40	12.463%	$37.5626	$37.56	$37.55	$37.60
7 purchase totals =	$804.43		$885.4266	$885.42	$885.45	$885.40