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	$61.70	6.388%	$65.6414	$65.64	$65.65	$65.60
Purchase #2	$146.96	7.727%	$158.3156	$158.32	$158.30	$158.30
Purchase #3	$215.72	5.497%	$227.5781	$227.58	$227.60	$227.60
Purchase #4	$208.32	12.381%	$234.1121	$234.11	$234.10	$234.10
Purchase #5	$249.56	5.595%	$263.5229	$263.52	$263.50	$263.50
Purchase #6	$180.87	8.778%	$196.7468	$196.75	$196.75	$196.70
Purchase #7	$228.67	12.268%	$256.7232	$256.72	$256.70	$256.70
7 purchase totals =	$1,291.80		$1,402.6401	$1,402.64	$1,402.60	$1,402.50