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	$95.92	6.843%	$102.4838	$102.48	$102.50	$102.50
Purchase #2	$82.49	9.394%	$90.2391	$90.24	$90.25	$90.20
Purchase #3	$238.83	12.805%	$269.4122	$269.41	$269.40	$269.40
Purchase #4	$239.84	6.574%	$255.6071	$255.61	$255.60	$255.60
Purchase #5	$109.83	3.744%	$113.942	$113.94	$113.95	$113.90
Purchase #6	$40.62	4.522%	$42.4568	$42.46	$42.45	$42.50
Purchase #7	$87.70	8.638%	$95.2755	$95.28	$95.30	$95.30
7 purchase totals =	$895.23		$969.4165	$969.42	$969.45	$969.40