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	$237.78	3.520%	$246.1499	$246.15	$246.15	$246.10
Purchase #2	$220.26	6.522%	$234.6254	$234.63	$234.65	$234.60
Purchase #3	$137.90	7.610%	$148.3942	$148.39	$148.40	$148.40
Purchase #4	$65.80	4.673%	$68.8748	$68.87	$68.85	$68.90
Purchase #5	$214.54	13.135%	$242.7198	$242.72	$242.70	$242.70
Purchase #6	$29.46	10.158%	$32.4525	$32.45	$32.45	$32.50
Purchase #7	$40.83	13.457%	$46.3245	$46.32	$46.30	$46.30
7 purchase totals =	$946.57		$1,019.5411	$1,019.53	$1,019.50	$1,019.50