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	$11.60	4.153%	$12.0817	$12.08	$12.10	$12.10
Purchase #2	$48.44	12.499%	$54.4945	$54.49	$54.50	$54.50
Purchase #3	$71.53	10.130%	$78.776	$78.78	$78.80	$78.80
Purchase #4	$105.59	10.379%	$116.5492	$116.55	$116.55	$116.50
Purchase #5	$146.48	5.217%	$154.1219	$154.12	$154.10	$154.10
Purchase #6	$63.35	13.858%	$72.129	$72.13	$72.15	$72.10
Purchase #7	$224.93	7.776%	$242.4206	$242.42	$242.40	$242.40
7 purchase totals =	$671.92		$730.5729	$730.57	$730.60	$730.50