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	$124.56	4.416%	$130.0606	$130.06	$130.05	$130.10
Purchase #2	$247.56	3.522%	$256.2791	$256.28	$256.30	$256.30
Purchase #3	$32.77	3.234%	$33.8298	$33.83	$33.85	$33.80
Purchase #4	$35.92	3.345%	$37.1215	$37.12	$37.10	$37.10
Purchase #5	$211.41	10.356%	$233.3036	$233.30	$233.30	$233.30
Purchase #6	$51.47	3.843%	$53.448	$53.45	$53.45	$53.40
Purchase #7	$157.85	5.252%	$166.1403	$166.14	$166.15	$166.10
7 purchase totals =	$861.54		$910.1829	$910.18	$910.20	$910.10