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	$166.55	10.366%	$183.8146	$183.81	$183.80	$183.80
Purchase #2	$158.35	10.683%	$175.2665	$175.27	$175.25	$175.30
Purchase #3	$184.61	8.469%	$200.2446	$200.24	$200.25	$200.20
Purchase #4	$109.53	12.831%	$123.5838	$123.58	$123.60	$123.60
Purchase #5	$132.56	8.777%	$144.1948	$144.19	$144.20	$144.20
Purchase #6	$67.95	5.242%	$71.5119	$71.51	$71.50	$71.50
Purchase #7	$161.30	8.501%	$175.0121	$175.01	$175.00	$175.00
7 purchase totals =	$980.85		$1,073.6283	$1,073.61	$1,073.60	$1,073.60