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	$170.35	4.735%	$178.4161	$178.42	$178.40	$178.40
Purchase #2	$7.51	5.295%	$7.9077	$7.91	$7.90	$7.90
Purchase #3	$38.66	10.650%	$42.7773	$42.78	$42.80	$42.80
Purchase #4	$65.67	13.104%	$74.2754	$74.28	$74.30	$74.30
Purchase #5	$248.38	13.500%	$281.9113	$281.91	$281.90	$281.90
Purchase #6	$215.38	8.577%	$233.8531	$233.85	$233.85	$233.90
Purchase #7	$157.86	9.760%	$173.2671	$173.27	$173.25	$173.30
7 purchase totals =	$903.81		$992.4080	$992.42	$992.40	$992.50