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	$59.37	4.846%	$62.2471	$62.25	$62.25	$62.20
Purchase #2	$96.90	8.798%	$105.4253	$105.43	$105.45	$105.40
Purchase #3	$78.76	13.138%	$89.1075	$89.11	$89.10	$89.10
Purchase #4	$42.45	4.338%	$44.2915	$44.29	$44.30	$44.30
Purchase #5	$230.77	8.539%	$250.4755	$250.48	$250.50	$250.50
Purchase #6	$243.58	11.726%	$272.1422	$272.14	$272.15	$272.10
Purchase #7	$218.41	13.502%	$247.8997	$247.90	$247.90	$247.90
7 purchase totals =	$970.24		$1,071.5888	$1,071.60	$1,071.65	$1,071.50