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	$177.47	10.451%	$196.0174	$196.02	$196.00	$196.00
Purchase #2	$176.51	6.377%	$187.766	$187.77	$187.75	$187.80
Purchase #3	$172.55	10.613%	$190.8627	$190.86	$190.85	$190.90
Purchase #4	$77.56	5.507%	$81.8312	$81.83	$81.85	$81.80
Purchase #5	$81.93	12.801%	$92.4179	$92.42	$92.40	$92.40
Purchase #6	$26.78	13.794%	$30.474	$30.47	$30.45	$30.50
Purchase #7	$178.84	4.745%	$187.326	$187.33	$187.35	$187.30
7 purchase totals =	$891.64		$966.6952	$966.70	$966.65	$966.70