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	$209.67	11.564%	$233.9162	$233.92	$233.90	$233.90
Purchase #2	$20.83	13.416%	$23.6246	$23.62	$23.60	$23.60
Purchase #3	$72.28	8.353%	$78.3175	$78.32	$78.30	$78.30
Purchase #4	$226.77	7.693%	$244.2154	$244.22	$244.20	$244.20
Purchase #5	$120.91	11.457%	$134.7627	$134.76	$134.75	$134.80
Purchase #6	$141.50	7.146%	$151.6116	$151.61	$151.60	$151.60
Purchase #7	$57.96	5.381%	$61.0788	$61.08	$61.10	$61.10
7 purchase totals =	$849.92		$927.5268	$927.53	$927.45	$927.50