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	$99.97	11.154%	$111.1207	$111.12	$111.10	$111.10
Purchase #2	$143.52	6.409%	$152.7182	$152.72	$152.70	$152.70
Purchase #3	$247.65	6.765%	$264.4035	$264.40	$264.40	$264.40
Purchase #4	$69.44	4.154%	$72.3245	$72.32	$72.30	$72.30
Purchase #5	$63.48	8.388%	$68.8047	$68.80	$68.80	$68.80
Purchase #6	$247.68	9.830%	$272.0269	$272.03	$272.05	$272.00
Purchase #7	$144.34	12.649%	$162.5976	$162.60	$162.60	$162.60
7 purchase totals =	$1,016.08		$1,103.9961	$1,103.99	$1,103.95	$1,103.90