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	$128.83	9.129%	$140.5909	$140.59	$140.60	$140.60
Purchase #2	$77.87	7.672%	$83.8442	$83.84	$83.85	$83.80
Purchase #3	$98.40	6.515%	$104.8108	$104.81	$104.80	$104.80
Purchase #4	$111.82	5.669%	$118.1591	$118.16	$118.15	$118.20
Purchase #5	$185.29	4.137%	$192.9554	$192.96	$192.95	$193.00
Purchase #6	$35.47	5.540%	$37.435	$37.44	$37.45	$37.40
Purchase #7	$44.55	6.636%	$47.5063	$47.51	$47.50	$47.50
7 purchase totals =	$682.23		$725.3017	$725.31	$725.30	$725.30