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	$96.73	6.485%	$103.0029	$103.00	$103.00	$103.00
Purchase #2	$172.39	9.495%	$188.7584	$188.76	$188.75	$188.80
Purchase #3	$160.40	8.383%	$173.8463	$173.85	$173.85	$173.80
Purchase #4	$236.69	8.115%	$255.8974	$255.90	$255.90	$255.90
Purchase #5	$44.98	5.636%	$47.5151	$47.52	$47.50	$47.50
Purchase #6	$90.60	12.657%	$102.0672	$102.07	$102.05	$102.10
Purchase #7	$136.47	11.425%	$152.0617	$152.06	$152.05	$152.10
7 purchase totals =	$938.26		$1,023.1490	$1,023.16	$1,023.10	$1,023.20