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	$53.82	10.649%	$59.5513	$59.55	$59.55	$59.60
Purchase #2	$156.30	10.789%	$173.1632	$173.16	$173.15	$173.20
Purchase #3	$127.30	13.706%	$144.7477	$144.75	$144.75	$144.70
Purchase #4	$213.54	5.441%	$225.1587	$225.16	$225.15	$225.20
Purchase #5	$185.48	13.266%	$210.0858	$210.09	$210.10	$210.10
Purchase #6	$192.81	4.422%	$201.3361	$201.34	$201.35	$201.30
Purchase #7	$90.42	13.430%	$102.5634	$102.56	$102.55	$102.60
7 purchase totals =	$1,019.67		$1,116.6062	$1,116.61	$1,116.60	$1,116.70