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	$122.38	5.763%	$129.4328	$129.43	$129.45	$129.40
Purchase #2	$189.75	3.375%	$196.1541	$196.15	$196.15	$196.20
Purchase #3	$87.61	12.213%	$98.3098	$98.31	$98.30	$98.30
Purchase #4	$180.49	11.578%	$201.3871	$201.39	$201.40	$201.40
Purchase #5	$145.38	11.476%	$162.0638	$162.06	$162.05	$162.10
Purchase #6	$105.71	5.435%	$111.4553	$111.46	$111.45	$111.50
Purchase #7	$180.68	13.250%	$204.6201	$204.62	$204.60	$204.60
7 purchase totals =	$1,012.00		$1,103.4230	$1,103.42	$1,103.40	$1,103.50