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	$217.83	5.624%	$230.0808	$230.08	$230.10	$230.10
Purchase #2	$168.78	9.168%	$184.2538	$184.25	$184.25	$184.30
Purchase #3	$157.91	7.761%	$170.1654	$170.17	$170.15	$170.20
Purchase #4	$191.66	9.735%	$210.3181	$210.32	$210.30	$210.30
Purchase #5	$122.50	6.784%	$130.8104	$130.81	$130.80	$130.80
Purchase #6	$83.91	6.576%	$89.4279	$89.43	$89.45	$89.40
Purchase #7	$216.41	11.280%	$240.821	$240.82	$240.80	$240.80
7 purchase totals =	$1,159.00		$1,255.8774	$1,255.88	$1,255.85	$1,255.90