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	$141.90	7.293%	$152.2488	$152.25	$152.25	$152.20
Purchase #2	$34.67	13.757%	$39.4396	$39.44	$39.45	$39.40
Purchase #3	$167.82	11.198%	$186.6125	$186.61	$186.60	$186.60
Purchase #4	$233.68	3.829%	$242.6276	$242.63	$242.65	$242.60
Purchase #5	$151.52	6.658%	$161.6082	$161.61	$161.60	$161.60
Purchase #6	$182.72	4.268%	$190.5185	$190.52	$190.50	$190.50
Purchase #7	$129.50	12.371%	$145.5204	$145.52	$145.50	$145.50
7 purchase totals =	$1,041.81		$1,118.5756	$1,118.58	$1,118.55	$1,118.40