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	$245.65	7.308%	$263.6021	$263.60	$263.60	$263.60
Purchase #2	$20.28	11.633%	$22.6392	$22.64	$22.65	$22.60
Purchase #3	$214.56	4.337%	$223.8655	$223.87	$223.85	$223.90
Purchase #4	$89.52	9.298%	$97.8436	$97.84	$97.85	$97.80
Purchase #5	$90.56	13.244%	$102.5538	$102.55	$102.55	$102.60
Purchase #6	$137.76	11.249%	$153.2566	$153.26	$153.25	$153.30
Purchase #7	$216.58	5.151%	$227.736	$227.74	$227.75	$227.70
7 purchase totals =	$1,014.91		$1,091.4968	$1,091.50	$1,091.50	$1,091.50