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	$89.47	6.490%	$95.2766	$95.28	$95.30	$95.30
Purchase #2	$235.36	5.406%	$248.0836	$248.08	$248.10	$248.10
Purchase #3	$232.26	10.478%	$256.5962	$256.60	$256.60	$256.60
Purchase #4	$43.35	4.642%	$45.3623	$45.36	$45.35	$45.40
Purchase #5	$79.97	10.225%	$88.1469	$88.15	$88.15	$88.10
Purchase #6	$203.61	9.723%	$223.407	$223.41	$223.40	$223.40
Purchase #7	$54.92	13.531%	$62.3512	$62.35	$62.35	$62.40
7 purchase totals =	$938.94		$1,019.2238	$1,019.23	$1,019.25	$1,019.30