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	$12.71	4.326%	$13.2598	$13.26	$13.25	$13.30
Purchase #2	$180.57	13.184%	$204.3763	$204.38	$204.40	$204.40
Purchase #3	$83.76	7.642%	$90.1609	$90.16	$90.15	$90.20
Purchase #4	$214.85	9.105%	$234.4121	$234.41	$234.40	$234.40
Purchase #5	$53.78	4.384%	$56.1377	$56.14	$56.15	$56.10
Purchase #6	$165.56	5.339%	$174.3992	$174.40	$174.40	$174.40
Purchase #7	$18.49	10.328%	$20.3996	$20.40	$20.40	$20.40
7 purchase totals =	$729.72		$793.1456	$793.15	$793.15	$793.20