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	$158.68	6.584%	$169.1275	$169.13	$169.15	$169.10
Purchase #2	$204.72	10.264%	$225.7325	$225.73	$225.75	$225.70
Purchase #3	$82.43	10.660%	$91.217	$91.22	$91.20	$91.20
Purchase #4	$236.47	13.163%	$267.5965	$267.60	$267.60	$267.60
Purchase #5	$43.27	5.513%	$45.6555	$45.66	$45.65	$45.70
Purchase #6	$50.60	8.396%	$54.8484	$54.85	$54.85	$54.80
Purchase #7	$82.45	8.591%	$89.5333	$89.53	$89.55	$89.50
7 purchase totals =	$858.62		$943.7107	$943.72	$943.75	$943.60