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	$52.29	13.800%	$59.506	$59.51	$59.50	$59.50
Purchase #2	$30.55	9.773%	$33.5357	$33.54	$33.55	$33.50
Purchase #3	$164.52	8.563%	$178.6078	$178.61	$178.60	$178.60
Purchase #4	$70.28	12.777%	$79.2597	$79.26	$79.25	$79.30
Purchase #5	$211.54	12.366%	$237.699	$237.70	$237.70	$237.70
Purchase #6	$212.54	9.867%	$233.5113	$233.51	$233.50	$233.50
Purchase #7	$30.75	6.480%	$32.7426	$32.74	$32.75	$32.70
7 purchase totals =	$772.47		$854.8621	$854.87	$854.85	$854.80