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	$130.73	10.411%	$144.3403	$144.34	$144.35	$144.30
Purchase #2	$211.84	12.617%	$238.5679	$238.57	$238.55	$238.60
Purchase #3	$132.58	5.485%	$139.852	$139.85	$139.85	$139.90
Purchase #4	$60.91	8.404%	$66.0289	$66.03	$66.05	$66.00
Purchase #5	$165.65	8.329%	$179.447	$179.45	$179.45	$179.40
Purchase #6	$79.85	13.245%	$90.4261	$90.43	$90.45	$90.40
Purchase #7	$177.93	7.362%	$191.0292	$191.03	$191.05	$191.00
7 purchase totals =	$959.49		$1,049.6914	$1,049.70	$1,049.75	$1,049.60