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	$138.80	9.711%	$152.2789	$152.28	$152.30	$152.30
Purchase #2	$208.43	6.734%	$222.4657	$222.47	$222.45	$222.50
Purchase #3	$140.27	11.504%	$156.4067	$156.41	$156.40	$156.40
Purchase #4	$123.31	13.707%	$140.2121	$140.21	$140.20	$140.20
Purchase #5	$205.88	5.459%	$217.119	$217.12	$217.10	$217.10
Purchase #6	$135.83	6.125%	$144.1496	$144.15	$144.15	$144.10
Purchase #7	$102.88	12.795%	$116.0435	$116.04	$116.05	$116.00
7 purchase totals =	$1,055.40		$1,148.6755	$1,148.68	$1,148.65	$1,148.60