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	$208.86	6.413%	$222.2542	$222.25	$222.25	$222.30
Purchase #2	$233.56	7.720%	$251.5908	$251.59	$251.60	$251.60
Purchase #3	$61.31	7.853%	$66.1247	$66.12	$66.10	$66.10
Purchase #4	$12.84	12.167%	$14.4022	$14.40	$14.40	$14.40
Purchase #5	$245.81	9.259%	$268.5695	$268.57	$268.55	$268.60
Purchase #6	$119.80	3.314%	$123.7702	$123.77	$123.75	$123.80
Purchase #7	$206.40	13.169%	$233.5808	$233.58	$233.60	$233.60
7 purchase totals =	$1,088.58		$1,180.2924	$1,180.28	$1,180.25	$1,180.40