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	$244.99	9.604%	$268.5188	$268.52	$268.50	$268.50
Purchase #2	$109.79	12.743%	$123.7805	$123.78	$123.80	$123.80
Purchase #3	$165.46	4.302%	$172.5781	$172.58	$172.60	$172.60
Purchase #4	$152.49	3.652%	$158.0589	$158.06	$158.05	$158.10
Purchase #5	$21.49	4.766%	$22.5142	$22.51	$22.50	$22.50
Purchase #6	$80.48	7.448%	$86.4742	$86.47	$86.45	$86.50
Purchase #7	$198.68	10.112%	$218.7705	$218.77	$218.75	$218.80
7 purchase totals =	$973.38		$1,050.6952	$1,050.69	$1,050.65	$1,050.80