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	$172.29	10.598%	$190.5493	$190.55	$190.55	$190.50
Purchase #2	$230.53	12.174%	$258.5947	$258.59	$258.60	$258.60
Purchase #3	$152.42	5.808%	$161.2726	$161.27	$161.25	$161.30
Purchase #4	$44.44	13.369%	$50.3812	$50.38	$50.40	$50.40
Purchase #5	$209.30	5.499%	$220.8094	$220.81	$220.80	$220.80
Purchase #6	$78.56	11.625%	$87.6926	$87.69	$87.70	$87.70
Purchase #7	$126.32	4.225%	$131.657	$131.66	$131.65	$131.70
7 purchase totals =	$1,013.86		$1,100.9568	$1,100.95	$1,100.95	$1,101.00