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	$72.32	10.831%	$80.153	$80.15	$80.15	$80.20
Purchase #2	$162.77	12.806%	$183.6143	$183.61	$183.60	$183.60
Purchase #3	$102.60	3.145%	$105.8268	$105.83	$105.85	$105.80
Purchase #4	$87.78	7.502%	$94.3653	$94.37	$94.35	$94.40
Purchase #5	$148.97	12.728%	$167.9309	$167.93	$167.95	$167.90
Purchase #6	$171.83	9.707%	$188.5095	$188.51	$188.50	$188.50
Purchase #7	$79.95	9.385%	$87.4533	$87.45	$87.45	$87.50
7 purchase totals =	$826.22		$907.8531	$907.85	$907.85	$907.90