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	$151.35	5.223%	$159.255	$159.26	$159.25	$159.30
Purchase #2	$164.72	3.743%	$170.8855	$170.89	$170.90	$170.90
Purchase #3	$42.34	9.510%	$46.3665	$46.37	$46.35	$46.40
Purchase #4	$223.46	12.131%	$250.5679	$250.57	$250.55	$250.60
Purchase #5	$245.46	10.854%	$272.1022	$272.10	$272.10	$272.10
Purchase #6	$243.78	4.688%	$255.2084	$255.21	$255.20	$255.20
Purchase #7	$11.29	13.160%	$12.7758	$12.78	$12.80	$12.80
7 purchase totals =	$1,082.40		$1,167.1613	$1,167.18	$1,167.15	$1,167.30