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	$144.86	4.495%	$151.3715	$151.37	$151.35	$151.40
Purchase #2	$25.83	13.376%	$29.285	$29.29	$29.30	$29.30
Purchase #3	$16.52	11.551%	$18.4282	$18.43	$18.45	$18.40
Purchase #4	$143.84	10.657%	$159.169	$159.17	$159.15	$159.20
Purchase #5	$73.78	12.272%	$82.8343	$82.83	$82.85	$82.80
Purchase #6	$179.82	5.839%	$190.3197	$190.32	$190.30	$190.30
Purchase #7	$38.53	13.447%	$43.7111	$43.71	$43.70	$43.70
7 purchase totals =	$623.18		$675.1188	$675.12	$675.10	$675.10