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	$194.60	7.580%	$209.3507	$209.35	$209.35	$209.40
Purchase #2	$48.27	13.169%	$54.6267	$54.63	$54.65	$54.60
Purchase #3	$137.90	13.574%	$156.6185	$156.62	$156.60	$156.60
Purchase #4	$40.84	5.707%	$43.1707	$43.17	$43.15	$43.20
Purchase #5	$245.67	12.172%	$275.573	$275.57	$275.55	$275.60
Purchase #6	$60.72	6.130%	$64.4421	$64.44	$64.45	$64.40
Purchase #7	$26.77	13.643%	$30.4222	$30.42	$30.40	$30.40
7 purchase totals =	$754.77		$834.2039	$834.20	$834.15	$834.20