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	$138.68	3.443%	$143.4548	$143.45	$143.45	$143.50
Purchase #2	$20.73	4.407%	$21.6436	$21.64	$21.65	$21.60
Purchase #3	$38.91	12.133%	$43.631	$43.63	$43.65	$43.60
Purchase #4	$16.77	12.430%	$18.8545	$18.85	$18.85	$18.90
Purchase #5	$225.40	13.178%	$255.1032	$255.10	$255.10	$255.10
Purchase #6	$147.46	5.512%	$155.588	$155.59	$155.60	$155.60
Purchase #7	$101.52	7.370%	$109.002	$109.00	$109.00	$109.00
7 purchase totals =	$689.47		$747.2771	$747.26	$747.30	$747.30