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	$38.79	12.168%	$43.51	$43.51	$43.50	$43.50
Purchase #2	$219.73	13.598%	$249.6089	$249.61	$249.60	$249.60
Purchase #3	$143.67	4.125%	$149.5964	$149.60	$149.60	$149.60
Purchase #4	$130.99	10.221%	$144.3785	$144.38	$144.40	$144.40
Purchase #5	$198.92	9.724%	$218.263	$218.26	$218.25	$218.30
Purchase #6	$167.52	11.302%	$186.4531	$186.45	$186.45	$186.50
Purchase #7	$144.41	10.324%	$159.3189	$159.32	$159.30	$159.30
7 purchase totals =	$1,044.03		$1,151.1288	$1,151.13	$1,151.10	$1,151.20