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	$103.99	11.224%	$115.6618	$115.66	$115.65	$115.70
Purchase #2	$152.75	10.763%	$169.1905	$169.19	$169.20	$169.20
Purchase #3	$241.43	9.604%	$264.6169	$264.62	$264.60	$264.60
Purchase #4	$182.72	9.196%	$199.5229	$199.52	$199.50	$199.50
Purchase #5	$118.99	12.113%	$133.4033	$133.40	$133.40	$133.40
Purchase #6	$100.99	10.497%	$111.5909	$111.59	$111.60	$111.60
Purchase #7	$21.27	4.176%	$22.1582	$22.16	$22.15	$22.20
7 purchase totals =	$922.14		$1,016.1445	$1,016.14	$1,016.10	$1,016.20