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	$242.83	3.427%	$251.1518	$251.15	$251.15	$251.20
Purchase #2	$66.47	11.733%	$74.2689	$74.27	$74.25	$74.30
Purchase #3	$71.53	5.301%	$75.3218	$75.32	$75.30	$75.30
Purchase #4	$60.44	4.674%	$63.265	$63.27	$63.25	$63.30
Purchase #5	$120.59	3.307%	$124.5779	$124.58	$124.60	$124.60
Purchase #6	$94.45	11.846%	$105.6385	$105.64	$105.65	$105.60
Purchase #7	$98.97	12.751%	$111.5897	$111.59	$111.60	$111.60
7 purchase totals =	$755.28		$805.8136	$805.82	$805.80	$805.90