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	$158.39	10.396%	$174.8562	$174.86	$174.85	$174.90
Purchase #2	$172.26	10.270%	$189.9511	$189.95	$189.95	$190.00
Purchase #3	$149.39	3.669%	$154.8711	$154.87	$154.85	$154.90
Purchase #4	$193.54	6.154%	$205.4505	$205.45	$205.45	$205.50
Purchase #5	$180.58	5.124%	$189.8329	$189.83	$189.85	$189.80
Purchase #6	$94.41	6.385%	$100.4381	$100.44	$100.45	$100.40
Purchase #7	$62.37	5.335%	$65.6974	$65.70	$65.70	$65.70
7 purchase totals =	$1,010.94		$1,081.0973	$1,081.10	$1,081.10	$1,081.20