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	$162.78	12.350%	$182.8833	$182.88	$182.90	$182.90
Purchase #2	$156.85	9.746%	$172.1366	$172.14	$172.15	$172.10
Purchase #3	$14.47	9.415%	$15.8324	$15.83	$15.85	$15.80
Purchase #4	$113.30	7.786%	$122.1215	$122.12	$122.10	$122.10
Purchase #5	$210.43	7.145%	$225.4652	$225.47	$225.45	$225.50
Purchase #6	$146.89	13.701%	$167.0154	$167.02	$167.00	$167.00
Purchase #7	$120.91	8.694%	$131.4219	$131.42	$131.40	$131.40
7 purchase totals =	$925.63		$1,016.8763	$1,016.88	$1,016.85	$1,016.80