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	$65.39	3.289%	$67.5407	$67.54	$67.55	$67.50
Purchase #2	$71.51	13.617%	$81.2475	$81.25	$81.25	$81.20
Purchase #3	$208.88	10.565%	$230.9482	$230.95	$230.95	$230.90
Purchase #4	$175.31	5.360%	$184.7066	$184.71	$184.70	$184.70
Purchase #5	$32.54	7.248%	$34.8985	$34.90	$34.90	$34.90
Purchase #6	$155.88	6.247%	$165.6178	$165.62	$165.60	$165.60
Purchase #7	$19.27	10.441%	$21.282	$21.28	$21.30	$21.30
7 purchase totals =	$728.78		$786.2413	$786.25	$786.25	$786.10