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	$30.87	4.573%	$32.2817	$32.28	$32.30	$32.30
Purchase #2	$227.55	6.447%	$242.2201	$242.22	$242.20	$242.20
Purchase #3	$111.91	13.621%	$127.1533	$127.15	$127.15	$127.20
Purchase #4	$119.95	10.828%	$132.9382	$132.94	$132.95	$132.90
Purchase #5	$185.90	7.680%	$200.1771	$200.18	$200.20	$200.20
Purchase #6	$97.98	6.651%	$104.4966	$104.50	$104.50	$104.50
Purchase #7	$95.98	12.809%	$108.2741	$108.27	$108.25	$108.30
7 purchase totals =	$870.14		$947.5411	$947.54	$947.55	$947.60