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	$17.60	10.175%	$19.3908	$19.39	$19.40	$19.40
Purchase #2	$78.86	13.773%	$89.7214	$89.72	$89.70	$89.70
Purchase #3	$170.92	13.456%	$193.919	$193.92	$193.90	$193.90
Purchase #4	$111.70	11.729%	$124.8013	$124.80	$124.80	$124.80
Purchase #5	$246.96	7.868%	$266.3908	$266.39	$266.40	$266.40
Purchase #6	$49.30	12.647%	$55.535	$55.54	$55.55	$55.50
Purchase #7	$206.58	10.693%	$228.6696	$228.67	$228.65	$228.70
7 purchase totals =	$881.92		$978.4279	$978.43	$978.40	$978.40