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	$12.75	13.814%	$14.5113	$14.51	$14.50	$14.50
Purchase #2	$194.60	11.306%	$216.6015	$216.60	$216.60	$216.60
Purchase #3	$241.68	13.298%	$273.8186	$273.82	$273.80	$273.80
Purchase #4	$227.66	10.872%	$252.4112	$252.41	$252.40	$252.40
Purchase #5	$118.59	7.630%	$127.6384	$127.64	$127.65	$127.60
Purchase #6	$170.81	10.139%	$188.1284	$188.13	$188.15	$188.10
Purchase #7	$205.89	10.582%	$227.6773	$227.68	$227.70	$227.70
7 purchase totals =	$1,171.98		$1,300.7867	$1,300.79	$1,300.80	$1,300.70