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	$102.51	8.846%	$111.578	$111.58	$111.60	$111.60
Purchase #2	$233.87	4.117%	$243.4984	$243.50	$243.50	$243.50
Purchase #3	$226.35	7.274%	$242.8147	$242.81	$242.80	$242.80
Purchase #4	$240.91	8.519%	$261.4331	$261.43	$261.45	$261.40
Purchase #5	$133.42	11.410%	$148.6432	$148.64	$148.65	$148.60
Purchase #6	$180.52	5.584%	$190.6002	$190.60	$190.60	$190.60
Purchase #7	$83.97	13.754%	$95.5192	$95.52	$95.50	$95.50
7 purchase totals =	$1,201.55		$1,294.0868	$1,294.08	$1,294.10	$1,294.00