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	$144.98	8.715%	$157.615	$157.62	$157.60	$157.60
Purchase #2	$111.47	6.409%	$118.6141	$118.61	$118.60	$118.60
Purchase #3	$48.95	13.196%	$55.4094	$55.41	$55.40	$55.40
Purchase #4	$169.29	8.761%	$184.1215	$184.12	$184.10	$184.10
Purchase #5	$168.94	6.279%	$179.5477	$179.55	$179.55	$179.50
Purchase #6	$129.93	6.589%	$138.4911	$138.49	$138.50	$138.50
Purchase #7	$74.94	4.748%	$78.4982	$78.50	$78.50	$78.50
7 purchase totals =	$848.50		$912.2970	$912.30	$912.25	$912.20