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	$148.49	9.335%	$162.3515	$162.35	$162.35	$162.40
Purchase #2	$155.40	5.771%	$164.3681	$164.37	$164.35	$164.40
Purchase #3	$52.99	12.436%	$59.5798	$59.58	$59.60	$59.60
Purchase #4	$134.97	3.103%	$139.1581	$139.16	$139.15	$139.20
Purchase #5	$113.44	7.104%	$121.4988	$121.50	$121.50	$121.50
Purchase #6	$131.59	11.147%	$146.2583	$146.26	$146.25	$146.30
Purchase #7	$233.55	3.112%	$240.8181	$240.82	$240.80	$240.80
7 purchase totals =	$970.43		$1,034.0327	$1,034.04	$1,034.00	$1,034.20