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	$146.93	9.809%	$161.3424	$161.34	$161.35	$161.30
Purchase #2	$202.27	11.853%	$226.2451	$226.25	$226.25	$226.20
Purchase #3	$174.27	10.498%	$192.5649	$192.56	$192.55	$192.60
Purchase #4	$243.43	4.783%	$255.0733	$255.07	$255.05	$255.10
Purchase #5	$43.31	4.648%	$45.323	$45.32	$45.30	$45.30
Purchase #6	$93.96	10.250%	$103.5909	$103.59	$103.60	$103.60
Purchase #7	$100.83	3.500%	$104.3591	$104.36	$104.35	$104.40
7 purchase totals =	$1,005.00		$1,088.4987	$1,088.49	$1,088.45	$1,088.50