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	$9.42	11.143%	$10.4697	$10.47	$10.45	$10.50
Purchase #2	$49.41	10.373%	$54.5353	$54.54	$54.55	$54.50
Purchase #3	$45.67	4.792%	$47.8585	$47.86	$47.85	$47.90
Purchase #4	$243.73	13.817%	$277.4062	$277.41	$277.40	$277.40
Purchase #5	$241.52	10.839%	$267.6984	$267.70	$267.70	$267.70
Purchase #6	$100.70	4.518%	$105.2496	$105.25	$105.25	$105.20
Purchase #7	$230.78	4.482%	$241.1236	$241.12	$241.10	$241.10
7 purchase totals =	$921.23		$1,004.3413	$1,004.35	$1,004.30	$1,004.30