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	$162.49	11.554%	$181.2641	$181.26	$181.25	$181.30
Purchase #2	$211.47	6.845%	$225.9451	$225.95	$225.95	$225.90
Purchase #3	$245.42	3.233%	$253.3544	$253.35	$253.35	$253.40
Purchase #4	$153.77	8.515%	$166.8635	$166.86	$166.85	$166.90
Purchase #5	$54.25	13.357%	$61.4962	$61.50	$61.50	$61.50
Purchase #6	$92.85	13.393%	$105.2854	$105.29	$105.30	$105.30
Purchase #7	$87.41	13.748%	$99.4271	$99.43	$99.45	$99.40
7 purchase totals =	$1,007.66		$1,093.6358	$1,093.64	$1,093.65	$1,093.70