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	$84.38	10.723%	$93.4281	$93.43	$93.45	$93.40
Purchase #2	$29.47	5.296%	$31.0307	$31.03	$31.05	$31.00
Purchase #3	$27.30	7.845%	$29.4417	$29.44	$29.45	$29.40
Purchase #4	$82.96	5.631%	$87.6315	$87.63	$87.65	$87.60
Purchase #5	$127.27	11.190%	$141.5115	$141.51	$141.50	$141.50
Purchase #6	$91.71	9.673%	$100.5811	$100.58	$100.60	$100.60
Purchase #7	$57.47	6.374%	$61.1331	$61.13	$61.15	$61.10
7 purchase totals =	$500.56		$544.7577	$544.75	$544.85	$544.60