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	$41.84	11.225%	$46.5365	$46.54	$46.55	$46.50
Purchase #2	$244.56	6.134%	$259.5613	$259.56	$259.55	$259.60
Purchase #3	$113.28	12.723%	$127.6926	$127.69	$127.70	$127.70
Purchase #4	$50.52	3.555%	$52.316	$52.32	$52.30	$52.30
Purchase #5	$31.25	5.866%	$33.0831	$33.08	$33.10	$33.10
Purchase #6	$230.52	4.577%	$241.0709	$241.07	$241.05	$241.10
Purchase #7	$37.40	7.813%	$40.3221	$40.32	$40.30	$40.30
7 purchase totals =	$749.37		$800.5825	$800.58	$800.55	$800.60