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	$152.49	13.586%	$173.2073	$173.21	$173.20	$173.20
Purchase #2	$13.34	7.395%	$14.3265	$14.33	$14.35	$14.30
Purchase #3	$137.75	4.266%	$143.6264	$143.63	$143.65	$143.60
Purchase #4	$124.30	8.297%	$134.6132	$134.61	$134.60	$134.60
Purchase #5	$54.57	8.332%	$59.1168	$59.12	$59.10	$59.10
Purchase #6	$79.87	11.581%	$89.1197	$89.12	$89.10	$89.10
Purchase #7	$232.64	8.813%	$253.1426	$253.14	$253.15	$253.10
7 purchase totals =	$794.96		$867.1525	$867.16	$867.15	$867.00