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	$63.95	13.794%	$72.7713	$72.77	$72.75	$72.80
Purchase #2	$88.86	10.769%	$98.4293	$98.43	$98.45	$98.40
Purchase #3	$83.43	9.462%	$91.3241	$91.32	$91.30	$91.30
Purchase #4	$94.38	10.448%	$104.2408	$104.24	$104.25	$104.20
Purchase #5	$87.63	4.581%	$91.6443	$91.64	$91.65	$91.60
Purchase #6	$147.58	7.565%	$158.7444	$158.74	$158.75	$158.70
Purchase #7	$109.95	6.859%	$117.4915	$117.49	$117.50	$117.50
7 purchase totals =	$675.78		$734.6457	$734.63	$734.65	$734.50