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	$94.74	7.343%	$101.6968	$101.70	$101.70	$101.70
Purchase #2	$91.29	8.548%	$99.0935	$99.09	$99.10	$99.10
Purchase #3	$114.81	10.602%	$126.9822	$126.98	$127.00	$127.00
Purchase #4	$233.88	11.315%	$260.3435	$260.34	$260.35	$260.30
Purchase #5	$94.31	9.761%	$103.5156	$103.52	$103.50	$103.50
Purchase #6	$9.86	6.665%	$10.5172	$10.52	$10.50	$10.50
Purchase #7	$129.32	10.266%	$142.596	$142.60	$142.60	$142.60
7 purchase totals =	$768.21		$844.7448	$844.75	$844.75	$844.70