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	$9.85	10.254%	$10.86	$10.86	$10.85	$10.90
Purchase #2	$89.67	12.170%	$100.5828	$100.58	$100.60	$100.60
Purchase #3	$162.44	10.709%	$179.8357	$179.84	$179.85	$179.80
Purchase #4	$205.31	13.166%	$232.3411	$232.34	$232.35	$232.30
Purchase #5	$123.88	11.865%	$138.5784	$138.58	$138.60	$138.60
Purchase #6	$99.52	10.754%	$110.2224	$110.22	$110.20	$110.20
Purchase #7	$80.68	11.570%	$90.0147	$90.01	$90.00	$90.00
7 purchase totals =	$771.35		$862.4351	$862.43	$862.45	$862.40