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	$76.80	13.231%	$86.9614	$86.96	$86.95	$87.00
Purchase #2	$77.71	7.321%	$83.3991	$83.40	$83.40	$83.40
Purchase #3	$35.91	7.204%	$38.497	$38.50	$38.50	$38.50
Purchase #4	$64.76	9.690%	$71.0352	$71.04	$71.05	$71.00
Purchase #5	$199.94	11.106%	$222.1453	$222.15	$222.15	$222.10
Purchase #6	$216.46	3.632%	$224.3218	$224.32	$224.30	$224.30
Purchase #7	$159.52	10.405%	$176.1181	$176.12	$176.10	$176.10
7 purchase totals =	$831.10		$902.4779	$902.49	$902.45	$902.40