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	$120.78	8.755%	$131.3543	$131.35	$131.35	$131.40
Purchase #2	$9.28	9.433%	$10.1554	$10.16	$10.15	$10.20
Purchase #3	$80.92	12.342%	$90.9071	$90.91	$90.90	$90.90
Purchase #4	$167.37	3.112%	$172.5786	$172.58	$172.60	$172.60
Purchase #5	$46.82	7.651%	$50.4022	$50.40	$50.40	$50.40
Purchase #6	$29.62	9.469%	$32.4247	$32.42	$32.40	$32.40
Purchase #7	$83.32	7.137%	$89.2665	$89.27	$89.25	$89.30
7 purchase totals =	$538.11		$577.0888	$577.09	$577.05	$577.20