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	$91.61	8.767%	$99.6414	$99.64	$99.65	$99.60
Purchase #2	$127.89	6.705%	$136.465	$136.47	$136.45	$136.50
Purchase #3	$99.47	8.540%	$107.9647	$107.96	$107.95	$108.00
Purchase #4	$151.41	13.693%	$172.1426	$172.14	$172.15	$172.10
Purchase #5	$199.42	13.204%	$225.7514	$225.75	$225.75	$225.80
Purchase #6	$247.80	3.173%	$255.6627	$255.66	$255.65	$255.70
Purchase #7	$97.96	11.727%	$109.4478	$109.45	$109.45	$109.40
7 purchase totals =	$1,015.56		$1,107.0756	$1,107.07	$1,107.05	$1,107.10