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	$71.71	12.490%	$80.6666	$80.67	$80.65	$80.70
Purchase #2	$180.98	10.632%	$200.2218	$200.22	$200.20	$200.20
Purchase #3	$107.70	13.739%	$122.4969	$122.50	$122.50	$122.50
Purchase #4	$136.98	6.763%	$146.244	$146.24	$146.25	$146.20
Purchase #5	$214.91	11.128%	$238.8252	$238.83	$238.85	$238.80
Purchase #6	$77.34	6.633%	$82.47	$82.47	$82.45	$82.50
Purchase #7	$172.61	11.780%	$192.9435	$192.94	$192.95	$192.90
7 purchase totals =	$962.23		$1,063.8680	$1,063.87	$1,063.85	$1,063.80