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	$163.54	7.362%	$175.5798	$175.58	$175.60	$175.60
Purchase #2	$161.44	11.135%	$179.4163	$179.42	$179.40	$179.40
Purchase #3	$126.51	10.173%	$139.3799	$139.38	$139.40	$139.40
Purchase #4	$176.62	4.277%	$184.174	$184.17	$184.15	$184.20
Purchase #5	$235.38	3.176%	$242.8557	$242.86	$242.85	$242.90
Purchase #6	$100.50	3.421%	$103.9381	$103.94	$103.95	$103.90
Purchase #7	$48.78	7.111%	$52.2487	$52.25	$52.25	$52.20
7 purchase totals =	$1,012.77		$1,077.5925	$1,077.60	$1,077.60	$1,077.60