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	$193.99	12.642%	$218.5142	$218.51	$218.50	$218.50
Purchase #2	$223.59	11.245%	$248.7327	$248.73	$248.75	$248.70
Purchase #3	$241.70	7.193%	$259.0855	$259.09	$259.10	$259.10
Purchase #4	$136.83	8.618%	$148.622	$148.62	$148.60	$148.60
Purchase #5	$195.66	13.717%	$222.4987	$222.50	$222.50	$222.50
Purchase #6	$180.71	10.813%	$200.2502	$200.25	$200.25	$200.30
Purchase #7	$87.33	3.715%	$90.5743	$90.57	$90.55	$90.60
7 purchase totals =	$1,259.81		$1,388.2776	$1,388.27	$1,388.25	$1,388.30