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	$92.27	8.516%	$100.1277	$100.13	$100.15	$100.10
Purchase #2	$193.81	13.546%	$220.0635	$220.06	$220.05	$220.10
Purchase #3	$9.95	3.414%	$10.2897	$10.29	$10.30	$10.30
Purchase #4	$96.36	9.460%	$105.4757	$105.48	$105.50	$105.50
Purchase #5	$111.32	5.388%	$117.3179	$117.32	$117.30	$117.30
Purchase #6	$250.45	3.575%	$259.4036	$259.40	$259.40	$259.40
Purchase #7	$247.95	6.843%	$264.9172	$264.92	$264.90	$264.90
7 purchase totals =	$1,002.11		$1,077.5953	$1,077.60	$1,077.60	$1,077.60