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	$42.54	12.641%	$47.9175	$47.92	$47.90	$47.90
Purchase #2	$151.27	9.471%	$165.5968	$165.60	$165.60	$165.60
Purchase #3	$90.42	13.733%	$102.8374	$102.84	$102.85	$102.80
Purchase #4	$62.79	5.240%	$66.0802	$66.08	$66.10	$66.10
Purchase #5	$189.89	9.276%	$207.5042	$207.50	$207.50	$207.50
Purchase #6	$187.52	12.792%	$211.5076	$211.51	$211.50	$211.50
Purchase #7	$203.66	7.433%	$218.798	$218.80	$218.80	$218.80
7 purchase totals =	$928.09		$1,020.2417	$1,020.25	$1,020.25	$1,020.20