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	$78.37	10.323%	$86.4601	$86.46	$86.45	$86.50
Purchase #2	$241.78	13.603%	$274.6693	$274.67	$274.65	$274.70
Purchase #3	$151.60	13.751%	$172.4465	$172.45	$172.45	$172.40
Purchase #4	$52.84	7.448%	$56.7755	$56.78	$56.80	$56.80
Purchase #5	$85.25	9.777%	$93.5849	$93.58	$93.60	$93.60
Purchase #6	$19.37	5.857%	$20.5045	$20.50	$20.50	$20.50
Purchase #7	$18.36	4.313%	$19.1519	$19.15	$19.15	$19.20
7 purchase totals =	$647.57		$723.5927	$723.59	$723.60	$723.70