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	$82.79	4.538%	$86.547	$86.55	$86.55	$86.50
Purchase #2	$21.30	4.200%	$22.1946	$22.19	$22.20	$22.20
Purchase #3	$126.64	13.840%	$144.167	$144.17	$144.15	$144.20
Purchase #4	$55.40	7.308%	$59.4486	$59.45	$59.45	$59.40
Purchase #5	$165.83	9.826%	$182.1245	$182.12	$182.10	$182.10
Purchase #6	$40.58	11.638%	$45.3027	$45.30	$45.30	$45.30
Purchase #7	$25.60	11.286%	$28.4892	$28.49	$28.50	$28.50
7 purchase totals =	$518.14		$568.2736	$568.27	$568.25	$568.20