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	$139.81	11.619%	$156.0545	$156.05	$156.05	$156.10
Purchase #2	$123.77	7.339%	$132.8535	$132.85	$132.85	$132.90
Purchase #3	$187.63	11.626%	$209.4439	$209.44	$209.45	$209.40
Purchase #4	$116.73	9.455%	$127.7668	$127.77	$127.75	$127.80
Purchase #5	$147.52	3.143%	$152.1566	$152.16	$152.15	$152.20
Purchase #6	$139.68	5.559%	$147.4448	$147.44	$147.45	$147.40
Purchase #7	$94.90	8.425%	$102.8953	$102.90	$102.90	$102.90
7 purchase totals =	$950.04		$1,028.6154	$1,028.61	$1,028.60	$1,028.70