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	$112.39	4.159%	$117.0643	$117.06	$117.05	$117.10
Purchase #2	$100.67	3.851%	$104.5468	$104.55	$104.55	$104.50
Purchase #3	$29.73	9.571%	$32.5755	$32.58	$32.60	$32.60
Purchase #4	$54.95	10.712%	$60.8362	$60.84	$60.85	$60.80
Purchase #5	$185.59	3.831%	$192.7	$192.70	$192.70	$192.70
Purchase #6	$100.46	13.809%	$114.3325	$114.33	$114.35	$114.30
Purchase #7	$95.39	4.840%	$100.0069	$100.01	$100.00	$100.00
7 purchase totals =	$679.18		$722.0622	$722.07	$722.10	$722.00