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	$228.60	11.397%	$254.6535	$254.65	$254.65	$254.70
Purchase #2	$225.70	8.457%	$244.7874	$244.79	$244.80	$244.80
Purchase #3	$49.43	10.668%	$54.7032	$54.70	$54.70	$54.70
Purchase #4	$96.89	13.312%	$109.788	$109.79	$109.80	$109.80
Purchase #5	$27.67	4.360%	$28.8764	$28.88	$28.90	$28.90
Purchase #6	$93.51	7.868%	$100.8674	$100.87	$100.85	$100.90
Purchase #7	$108.59	12.491%	$122.154	$122.15	$122.15	$122.20
7 purchase totals =	$830.39		$915.8299	$915.83	$915.85	$916.00