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	$85.32	10.275%	$94.0866	$94.09	$94.10	$94.10
Purchase #2	$91.56	12.389%	$102.9034	$102.90	$102.90	$102.90
Purchase #3	$154.59	3.367%	$159.795	$159.80	$159.80	$159.80
Purchase #4	$247.30	6.125%	$262.4471	$262.45	$262.45	$262.40
Purchase #5	$74.54	7.526%	$80.1499	$80.15	$80.15	$80.10
Purchase #6	$114.76	11.239%	$127.6579	$127.66	$127.65	$127.70
Purchase #7	$19.87	9.768%	$21.8109	$21.81	$21.80	$21.80
7 purchase totals =	$787.94		$848.8508	$848.86	$848.85	$848.80