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	$57.62	6.470%	$61.348	$61.35	$61.35	$61.30
Purchase #2	$40.39	11.672%	$45.1043	$45.10	$45.10	$45.10
Purchase #3	$59.86	8.340%	$64.8523	$64.85	$64.85	$64.90
Purchase #4	$94.79	9.271%	$103.578	$103.58	$103.60	$103.60
Purchase #5	$186.86	10.199%	$205.9179	$205.92	$205.90	$205.90
Purchase #6	$134.60	13.464%	$152.7225	$152.72	$152.70	$152.70
Purchase #7	$48.94	9.552%	$53.6147	$53.61	$53.60	$53.60
7 purchase totals =	$623.06		$687.1377	$687.13	$687.10	$687.10