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	$101.92	6.304%	$108.345	$108.35	$108.35	$108.30
Purchase #2	$127.53	5.562%	$134.6232	$134.62	$134.60	$134.60
Purchase #3	$174.78	12.428%	$196.5017	$196.50	$196.50	$196.50
Purchase #4	$60.48	3.672%	$62.7008	$62.70	$62.70	$62.70
Purchase #5	$80.81	7.830%	$87.1374	$87.14	$87.15	$87.10
Purchase #6	$95.91	8.460%	$104.024	$104.02	$104.00	$104.00
Purchase #7	$95.86	11.523%	$106.9059	$106.91	$106.90	$106.90
7 purchase totals =	$737.29		$800.2380	$800.24	$800.20	$800.10