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	$82.26	9.553%	$90.1183	$90.12	$90.10	$90.10
Purchase #2	$18.29	10.737%	$20.2538	$20.25	$20.25	$20.30
Purchase #3	$131.37	11.788%	$146.8559	$146.86	$146.85	$146.90
Purchase #4	$231.48	11.167%	$257.3294	$257.33	$257.35	$257.30
Purchase #5	$127.99	12.607%	$144.1257	$144.13	$144.15	$144.10
Purchase #6	$244.86	13.714%	$278.4401	$278.44	$278.45	$278.40
Purchase #7	$65.86	8.831%	$71.6761	$71.68	$71.70	$71.70
7 purchase totals =	$902.11		$1,008.7993	$1,008.81	$1,008.85	$1,008.80