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	$153.90	11.433%	$171.4954	$171.50	$171.50	$171.50
Purchase #2	$28.43	4.766%	$29.785	$29.79	$29.80	$29.80
Purchase #3	$153.54	7.834%	$165.5683	$165.57	$165.55	$165.60
Purchase #4	$181.31	5.114%	$190.5822	$190.58	$190.60	$190.60
Purchase #5	$117.87	8.267%	$127.6143	$127.61	$127.60	$127.60
Purchase #6	$119.65	9.258%	$130.7272	$130.73	$130.75	$130.70
Purchase #7	$67.31	13.450%	$76.3632	$76.36	$76.35	$76.40
7 purchase totals =	$822.01		$892.1356	$892.14	$892.15	$892.20