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	$62.83	5.766%	$66.4528	$66.45	$66.45	$66.50
Purchase #2	$141.37	3.486%	$146.2982	$146.30	$146.30	$146.30
Purchase #3	$141.73	4.513%	$148.1263	$148.13	$148.15	$148.10
Purchase #4	$106.39	4.766%	$111.4605	$111.46	$111.45	$111.50
Purchase #5	$232.48	5.767%	$245.8871	$245.89	$245.90	$245.90
Purchase #6	$202.93	6.248%	$215.6091	$215.61	$215.60	$215.60
Purchase #7	$226.95	9.261%	$247.9678	$247.97	$247.95	$248.00
7 purchase totals =	$1,114.68		$1,181.8018	$1,181.81	$1,181.80	$1,181.90