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	$165.92	13.446%	$188.2296	$188.23	$188.25	$188.20
Purchase #2	$151.88	13.599%	$172.5342	$172.53	$172.55	$172.50
Purchase #3	$13.81	4.457%	$14.4255	$14.43	$14.45	$14.40
Purchase #4	$171.57	12.589%	$193.1689	$193.17	$193.15	$193.20
Purchase #5	$128.25	13.530%	$145.6022	$145.60	$145.60	$145.60
Purchase #6	$52.82	11.503%	$58.8959	$58.90	$58.90	$58.90
Purchase #7	$223.63	7.521%	$240.4492	$240.45	$240.45	$240.40
7 purchase totals =	$907.88		$1,013.3055	$1,013.31	$1,013.35	$1,013.20