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	$241.72	12.600%	$272.1767	$272.18	$272.20	$272.20
Purchase #2	$141.92	10.226%	$156.4327	$156.43	$156.45	$156.40
Purchase #3	$114.90	10.772%	$127.277	$127.28	$127.30	$127.30
Purchase #4	$96.39	13.498%	$109.4007	$109.40	$109.40	$109.40
Purchase #5	$94.45	8.233%	$102.2261	$102.23	$102.25	$102.20
Purchase #6	$132.47	8.640%	$143.9154	$143.92	$143.90	$143.90
Purchase #7	$226.69	4.479%	$236.8434	$236.84	$236.85	$236.80
7 purchase totals =	$1,048.54		$1,148.2720	$1,148.28	$1,148.35	$1,148.20