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	$210.76	7.808%	$227.2161	$227.22	$227.20	$227.20
Purchase #2	$132.62	10.734%	$146.8554	$146.86	$146.85	$146.90
Purchase #3	$140.83	6.867%	$150.5008	$150.50	$150.50	$150.50
Purchase #4	$62.65	4.266%	$65.3226	$65.32	$65.30	$65.30
Purchase #5	$189.30	12.320%	$212.6218	$212.62	$212.60	$212.60
Purchase #6	$212.44	9.726%	$233.1019	$233.10	$233.10	$233.10
Purchase #7	$29.51	13.793%	$33.5803	$33.58	$33.60	$33.60
7 purchase totals =	$978.11		$1,069.1989	$1,069.20	$1,069.15	$1,069.20