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	$39.93	13.399%	$45.2802	$45.28	$45.30	$45.30
Purchase #2	$187.50	11.244%	$208.5825	$208.58	$208.60	$208.60
Purchase #3	$215.46	10.599%	$238.2966	$238.30	$238.30	$238.30
Purchase #4	$81.86	8.630%	$88.9245	$88.92	$88.90	$88.90
Purchase #5	$147.64	8.297%	$159.8897	$159.89	$159.90	$159.90
Purchase #6	$76.94	13.748%	$87.5177	$87.52	$87.50	$87.50
Purchase #7	$239.82	13.615%	$272.4715	$272.47	$272.45	$272.50
7 purchase totals =	$989.15		$1,100.9627	$1,100.96	$1,100.95	$1,101.00