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	$128.45	12.197%	$144.117	$144.12	$144.10	$144.10
Purchase #2	$136.44	7.164%	$146.2146	$146.21	$146.20	$146.20
Purchase #3	$149.80	3.106%	$154.4528	$154.45	$154.45	$154.50
Purchase #4	$86.33	3.173%	$89.0693	$89.07	$89.05	$89.10
Purchase #5	$241.29	8.788%	$262.4946	$262.49	$262.50	$262.50
Purchase #6	$176.53	6.554%	$188.0998	$188.10	$188.10	$188.10
Purchase #7	$199.45	3.230%	$205.8922	$205.89	$205.90	$205.90
7 purchase totals =	$1,118.29		$1,190.3403	$1,190.33	$1,190.30	$1,190.40