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	$150.79	10.653%	$166.8537	$166.85	$166.85	$166.90
Purchase #2	$46.77	4.773%	$49.0023	$49.00	$49.00	$49.00
Purchase #3	$63.96	11.792%	$71.5022	$71.50	$71.50	$71.50
Purchase #4	$41.74	10.149%	$45.9762	$45.98	$46.00	$46.00
Purchase #5	$61.67	13.373%	$69.9171	$69.92	$69.90	$69.90
Purchase #6	$62.29	6.652%	$66.4335	$66.43	$66.45	$66.40
Purchase #7	$55.95	11.516%	$62.3932	$62.39	$62.40	$62.40
7 purchase totals =	$483.17		$532.0782	$532.07	$532.10	$532.10