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	$49.38	13.763%	$56.1762	$56.18	$56.20	$56.20
Purchase #2	$139.34	13.729%	$158.47	$158.47	$158.45	$158.50
Purchase #3	$160.86	7.269%	$172.5529	$172.55	$172.55	$172.60
Purchase #4	$53.54	11.407%	$59.6473	$59.65	$59.65	$59.60
Purchase #5	$226.84	11.867%	$253.7591	$253.76	$253.75	$253.80
Purchase #6	$13.39	7.149%	$14.3473	$14.35	$14.35	$14.30
Purchase #7	$136.27	11.619%	$152.1032	$152.10	$152.10	$152.10
7 purchase totals =	$779.62		$867.0560	$867.06	$867.05	$867.10