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	$32.78	11.743%	$36.6294	$36.63	$36.65	$36.60
Purchase #2	$221.78	7.733%	$238.9302	$238.93	$238.95	$238.90
Purchase #3	$188.75	8.852%	$205.4582	$205.46	$205.45	$205.50
Purchase #4	$64.35	12.783%	$72.5759	$72.58	$72.60	$72.60
Purchase #5	$19.69	4.865%	$20.6479	$20.65	$20.65	$20.60
Purchase #6	$30.81	4.690%	$32.255	$32.26	$32.25	$32.30
Purchase #7	$141.35	9.715%	$155.0822	$155.08	$155.10	$155.10
7 purchase totals =	$699.51		$761.5788	$761.59	$761.65	$761.60