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	$69.95	4.248%	$72.9215	$72.92	$72.90	$72.90
Purchase #2	$201.87	13.630%	$229.3849	$229.38	$229.40	$229.40
Purchase #3	$82.82	9.719%	$90.8693	$90.87	$90.85	$90.90
Purchase #4	$117.87	3.532%	$122.0332	$122.03	$122.05	$122.00
Purchase #5	$179.33	8.348%	$194.3005	$194.30	$194.30	$194.30
Purchase #6	$178.93	8.640%	$194.3896	$194.39	$194.40	$194.40
Purchase #7	$100.47	10.813%	$111.3338	$111.33	$111.35	$111.30
7 purchase totals =	$931.24		$1,015.2328	$1,015.22	$1,015.25	$1,015.20