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	$245.42	3.860%	$254.8932	$254.89	$254.90	$254.90
Purchase #2	$228.83	10.633%	$253.1615	$253.16	$253.15	$253.20
Purchase #3	$118.51	11.617%	$132.2773	$132.28	$132.30	$132.30
Purchase #4	$171.41	4.356%	$178.8766	$178.88	$178.90	$178.90
Purchase #5	$157.60	8.860%	$171.5634	$171.56	$171.55	$171.60
Purchase #6	$248.56	6.422%	$264.5225	$264.52	$264.50	$264.50
Purchase #7	$103.35	8.516%	$112.1513	$112.15	$112.15	$112.20
7 purchase totals =	$1,273.68		$1,367.4458	$1,367.44	$1,367.45	$1,367.60