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	$61.53	5.822%	$65.1123	$65.11	$65.10	$65.10
Purchase #2	$74.81	6.624%	$79.7654	$79.77	$79.75	$79.80
Purchase #3	$182.46	12.713%	$205.6561	$205.66	$205.65	$205.70
Purchase #4	$72.71	13.618%	$82.6116	$82.61	$82.60	$82.60
Purchase #5	$85.46	13.779%	$97.2355	$97.24	$97.25	$97.20
Purchase #6	$71.37	9.683%	$78.2808	$78.28	$78.30	$78.30
Purchase #7	$132.59	8.236%	$143.5101	$143.51	$143.50	$143.50
7 purchase totals =	$680.93		$752.1718	$752.18	$752.15	$752.20