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	$110.53	11.673%	$123.4322	$123.43	$123.45	$123.40
Purchase #2	$54.69	5.667%	$57.7893	$57.79	$57.80	$57.80
Purchase #3	$58.61	4.295%	$61.1273	$61.13	$61.15	$61.10
Purchase #4	$10.51	6.466%	$11.1896	$11.19	$11.20	$11.20
Purchase #5	$156.33	13.580%	$177.5596	$177.56	$177.55	$177.60
Purchase #6	$142.30	11.144%	$158.1579	$158.16	$158.15	$158.20
Purchase #7	$66.69	11.395%	$74.2893	$74.29	$74.30	$74.30
7 purchase totals =	$599.66		$663.5452	$663.55	$663.60	$663.60