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	$145.53	4.787%	$152.4965	$152.50	$152.50	$152.50
Purchase #2	$19.75	10.603%	$21.8441	$21.84	$21.85	$21.80
Purchase #3	$247.40	12.766%	$278.9831	$278.98	$279.00	$279.00
Purchase #4	$152.52	13.465%	$173.0568	$173.06	$173.05	$173.10
Purchase #5	$124.97	11.690%	$139.579	$139.58	$139.60	$139.60
Purchase #6	$106.88	8.170%	$115.6121	$115.61	$115.60	$115.60
Purchase #7	$141.38	10.525%	$156.2602	$156.26	$156.25	$156.30
7 purchase totals =	$938.43		$1,037.8318	$1,037.83	$1,037.85	$1,037.90