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	$168.38	4.209%	$175.4671	$175.47	$175.45	$175.50
Purchase #2	$44.40	13.680%	$50.4739	$50.47	$50.45	$50.50
Purchase #3	$118.65	4.616%	$124.1269	$124.13	$124.15	$124.10
Purchase #4	$84.38	7.466%	$90.6798	$90.68	$90.70	$90.70
Purchase #5	$144.85	10.478%	$160.0274	$160.03	$160.05	$160.00
Purchase #6	$80.78	11.124%	$89.766	$89.77	$89.75	$89.80
Purchase #7	$132.83	10.108%	$146.2565	$146.26	$146.25	$146.30
7 purchase totals =	$774.27		$836.7976	$836.81	$836.80	$836.90