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	$150.79	11.585%	$168.259	$168.26	$168.25	$168.30
Purchase #2	$62.82	6.698%	$67.0277	$67.03	$67.05	$67.00
Purchase #3	$8.86	3.719%	$9.1895	$9.19	$9.20	$9.20
Purchase #4	$184.85	12.756%	$208.4295	$208.43	$208.45	$208.40
Purchase #5	$115.82	13.176%	$131.0804	$131.08	$131.10	$131.10
Purchase #6	$133.42	7.389%	$143.2784	$143.28	$143.30	$143.30
Purchase #7	$53.86	13.525%	$61.1446	$61.14	$61.15	$61.10
7 purchase totals =	$710.42		$788.4091	$788.41	$788.50	$788.40