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	$107.66	9.609%	$118.005	$118.01	$118.00	$118.00
Purchase #2	$82.28	8.668%	$89.412	$89.41	$89.40	$89.40
Purchase #3	$168.47	3.447%	$174.2772	$174.28	$174.30	$174.30
Purchase #4	$60.39	4.105%	$62.869	$62.87	$62.85	$62.90
Purchase #5	$182.31	5.754%	$192.8001	$192.80	$192.80	$192.80
Purchase #6	$88.66	11.833%	$99.1511	$99.15	$99.15	$99.20
Purchase #7	$122.62	11.151%	$136.2934	$136.29	$136.30	$136.30
7 purchase totals =	$812.39		$872.8078	$872.81	$872.80	$872.90