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	$97.86	13.613%	$111.1817	$111.18	$111.20	$111.20
Purchase #2	$168.70	7.678%	$181.6528	$181.65	$181.65	$181.70
Purchase #3	$13.74	4.727%	$14.3895	$14.39	$14.40	$14.40
Purchase #4	$50.78	7.177%	$54.4245	$54.42	$54.40	$54.40
Purchase #5	$75.69	6.229%	$80.4047	$80.40	$80.40	$80.40
Purchase #6	$112.74	3.775%	$116.9959	$117.00	$117.00	$117.00
Purchase #7	$246.54	4.158%	$256.7911	$256.79	$256.80	$256.80
7 purchase totals =	$766.05		$815.8402	$815.83	$815.85	$815.90