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	$152.38	4.447%	$159.1563	$159.16	$159.15	$159.20
Purchase #2	$116.51	4.428%	$121.6691	$121.67	$121.65	$121.70
Purchase #3	$30.69	13.517%	$34.8384	$34.84	$34.85	$34.80
Purchase #4	$94.39	10.815%	$104.5983	$104.60	$104.60	$104.60
Purchase #5	$144.55	4.107%	$150.4867	$150.49	$150.50	$150.50
Purchase #6	$38.38	10.616%	$42.4544	$42.45	$42.45	$42.50
Purchase #7	$62.98	3.462%	$65.1604	$65.16	$65.15	$65.20
7 purchase totals =	$639.88		$678.3636	$678.37	$678.35	$678.50