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	$196.74	11.496%	$219.3572	$219.36	$219.35	$219.40
Purchase #2	$63.56	4.861%	$66.6497	$66.65	$66.65	$66.60
Purchase #3	$191.27	6.786%	$204.2496	$204.25	$204.25	$204.20
Purchase #4	$53.46	10.634%	$59.1449	$59.14	$59.15	$59.10
Purchase #5	$41.72	11.269%	$46.4214	$46.42	$46.40	$46.40
Purchase #6	$94.65	11.340%	$105.3833	$105.38	$105.40	$105.40
Purchase #7	$10.32	13.522%	$11.7155	$11.72	$11.70	$11.70
7 purchase totals =	$651.72		$712.9216	$712.92	$712.90	$712.80