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	$104.64	7.526%	$112.5152	$112.52	$112.50	$112.50
Purchase #2	$11.45	10.257%	$12.6244	$12.62	$12.60	$12.60
Purchase #3	$216.25	11.496%	$241.1101	$241.11	$241.10	$241.10
Purchase #4	$40.30	5.219%	$42.4033	$42.40	$42.40	$42.40
Purchase #5	$154.42	7.473%	$165.9598	$165.96	$165.95	$166.00
Purchase #6	$106.59	6.111%	$113.1037	$113.10	$113.10	$113.10
Purchase #7	$109.33	7.868%	$117.9321	$117.93	$117.95	$117.90
7 purchase totals =	$742.98		$805.6486	$805.64	$805.60	$805.60