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	$247.38	11.389%	$275.5541	$275.55	$275.55	$275.60
Purchase #2	$90.40	7.515%	$97.1936	$97.19	$97.20	$97.20
Purchase #3	$66.52	7.654%	$71.6114	$71.61	$71.60	$71.60
Purchase #4	$20.50	8.620%	$22.2671	$22.27	$22.25	$22.30
Purchase #5	$15.83	10.171%	$17.4401	$17.44	$17.45	$17.40
Purchase #6	$102.96	6.705%	$109.8635	$109.86	$109.85	$109.90
Purchase #7	$169.94	6.647%	$181.2359	$181.24	$181.25	$181.20
7 purchase totals =	$713.53		$775.1657	$775.16	$775.15	$775.20