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	$62.66	6.773%	$66.904	$66.90	$66.90	$66.90
Purchase #2	$23.91	13.262%	$27.0809	$27.08	$27.10	$27.10
Purchase #3	$226.82	13.801%	$258.1234	$258.12	$258.10	$258.10
Purchase #4	$171.97	10.725%	$190.4138	$190.41	$190.40	$190.40
Purchase #5	$209.39	9.168%	$228.5869	$228.59	$228.60	$228.60
Purchase #6	$134.50	5.407%	$141.7724	$141.77	$141.75	$141.80
Purchase #7	$13.28	9.873%	$14.5911	$14.59	$14.60	$14.60
7 purchase totals =	$842.53		$927.4725	$927.46	$927.45	$927.50