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	$167.35	8.554%	$181.6651	$181.67	$181.65	$181.70
Purchase #2	$10.77	13.726%	$12.2483	$12.25	$12.25	$12.20
Purchase #3	$47.87	12.138%	$53.6805	$53.68	$53.70	$53.70
Purchase #4	$248.34	6.149%	$263.6104	$263.61	$263.60	$263.60
Purchase #5	$124.74	4.344%	$130.1587	$130.16	$130.15	$130.20
Purchase #6	$62.60	12.824%	$70.6278	$70.63	$70.65	$70.60
Purchase #7	$158.79	12.660%	$178.8928	$178.89	$178.90	$178.90
7 purchase totals =	$820.46		$890.8836	$890.89	$890.90	$890.90