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	$144.25	9.828%	$158.4269	$158.43	$158.45	$158.40
Purchase #2	$88.29	11.481%	$98.4266	$98.43	$98.45	$98.40
Purchase #3	$128.64	13.574%	$146.1016	$146.10	$146.10	$146.10
Purchase #4	$80.56	9.587%	$88.2833	$88.28	$88.30	$88.30
Purchase #5	$15.80	8.758%	$17.1838	$17.18	$17.20	$17.20
Purchase #6	$184.83	6.306%	$196.4854	$196.49	$196.50	$196.50
Purchase #7	$143.64	3.265%	$148.3298	$148.33	$148.35	$148.30
7 purchase totals =	$786.01		$853.2374	$853.24	$853.35	$853.20