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	$145.67	8.834%	$158.5385	$158.54	$158.55	$158.50
Purchase #2	$165.86	7.408%	$178.1469	$178.15	$178.15	$178.10
Purchase #3	$250.69	11.333%	$279.1007	$279.10	$279.10	$279.10
Purchase #4	$136.77	11.686%	$152.7529	$152.75	$152.75	$152.80
Purchase #5	$116.35	3.175%	$120.0441	$120.04	$120.05	$120.00
Purchase #6	$90.38	13.601%	$102.6726	$102.67	$102.65	$102.70
Purchase #7	$42.78	4.268%	$44.6059	$44.61	$44.60	$44.60
7 purchase totals =	$948.50		$1,035.8616	$1,035.86	$1,035.85	$1,035.80