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	$226.26	10.164%	$249.2571	$249.26	$249.25	$249.30
Purchase #2	$48.99	10.788%	$54.275	$54.28	$54.30	$54.30
Purchase #3	$235.83	11.170%	$262.1722	$262.17	$262.15	$262.20
Purchase #4	$100.84	4.593%	$105.4716	$105.47	$105.45	$105.50
Purchase #5	$153.67	5.723%	$162.4645	$162.46	$162.45	$162.50
Purchase #6	$85.46	6.823%	$91.2909	$91.29	$91.30	$91.30
Purchase #7	$199.58	6.543%	$212.6385	$212.64	$212.65	$212.60
7 purchase totals =	$1,050.63		$1,137.5698	$1,137.57	$1,137.55	$1,137.70