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	$10.78	7.530%	$11.5917	$11.59	$11.60	$11.60
Purchase #2	$9.47	8.847%	$10.3078	$10.31	$10.30	$10.30
Purchase #3	$49.80	5.402%	$52.4902	$52.49	$52.50	$52.50
Purchase #4	$25.48	11.342%	$28.3699	$28.37	$28.35	$28.40
Purchase #5	$228.53	12.427%	$256.9294	$256.93	$256.95	$256.90
Purchase #6	$9.52	9.410%	$10.4158	$10.42	$10.40	$10.40
Purchase #7	$24.65	13.144%	$27.89	$27.89	$27.90	$27.90
7 purchase totals =	$358.23		$397.9948	$398.00	$398.00	$398.00