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	$97.48	8.212%	$105.4851	$105.49	$105.50	$105.50
Purchase #2	$209.39	5.555%	$221.0216	$221.02	$221.00	$221.00
Purchase #3	$196.74	9.528%	$215.4854	$215.49	$215.50	$215.50
Purchase #4	$45.94	9.300%	$50.2124	$50.21	$50.20	$50.20
Purchase #5	$173.90	11.167%	$193.3194	$193.32	$193.30	$193.30
Purchase #6	$196.97	6.232%	$209.2452	$209.25	$209.25	$209.20
Purchase #7	$107.81	3.517%	$111.6017	$111.60	$111.60	$111.60
7 purchase totals =	$1,028.23		$1,106.3708	$1,106.38	$1,106.35	$1,106.30