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	$22.93	11.731%	$25.6199	$25.62	$25.60	$25.60
Purchase #2	$71.78	13.516%	$81.4818	$81.48	$81.50	$81.50
Purchase #3	$192.51	13.113%	$217.7538	$217.75	$217.75	$217.80
Purchase #4	$73.51	12.138%	$82.4326	$82.43	$82.45	$82.40
Purchase #5	$229.79	11.477%	$256.163	$256.16	$256.15	$256.20
Purchase #6	$136.65	4.353%	$142.5984	$142.60	$142.60	$142.60
Purchase #7	$152.97	7.295%	$164.1292	$164.13	$164.15	$164.10
7 purchase totals =	$880.14		$970.1787	$970.17	$970.20	$970.20