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	$147.35	10.279%	$162.4961	$162.50	$162.50	$162.50
Purchase #2	$115.88	6.668%	$123.6069	$123.61	$123.60	$123.60
Purchase #3	$225.95	12.631%	$254.4897	$254.49	$254.50	$254.50
Purchase #4	$183.91	13.535%	$208.8022	$208.80	$208.80	$208.80
Purchase #5	$149.60	5.602%	$157.9806	$157.98	$158.00	$158.00
Purchase #6	$69.53	11.778%	$77.7192	$77.72	$77.70	$77.70
Purchase #7	$115.48	9.781%	$126.7751	$126.78	$126.80	$126.80
7 purchase totals =	$1,007.70		$1,111.8698	$1,111.88	$1,111.90	$1,111.90