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	$134.97	13.316%	$152.9426	$152.94	$152.95	$152.90
Purchase #2	$215.56	9.433%	$235.8938	$235.89	$235.90	$235.90
Purchase #3	$138.55	3.286%	$143.1028	$143.10	$143.10	$143.10
Purchase #4	$234.94	11.582%	$262.1508	$262.15	$262.15	$262.20
Purchase #5	$15.54	8.317%	$16.8325	$16.83	$16.85	$16.80
Purchase #6	$117.55	8.791%	$127.8838	$127.88	$127.90	$127.90
Purchase #7	$143.60	12.813%	$161.9995	$162.00	$162.00	$162.00
7 purchase totals =	$1,000.71		$1,100.8058	$1,100.79	$1,100.85	$1,100.80