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	$98.43	10.592%	$108.8557	$108.86	$108.85	$108.90
Purchase #2	$42.34	4.109%	$44.0798	$44.08	$44.10	$44.10
Purchase #3	$68.92	13.537%	$78.2497	$78.25	$78.25	$78.20
Purchase #4	$37.51	13.434%	$42.5491	$42.55	$42.55	$42.50
Purchase #5	$11.57	9.231%	$12.638	$12.64	$12.65	$12.60
Purchase #6	$7.69	11.872%	$8.603	$8.60	$8.60	$8.60
Purchase #7	$175.79	12.683%	$198.0854	$198.09	$198.10	$198.10
7 purchase totals =	$442.25		$493.0607	$493.07	$493.10	$493.00