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	$228.58	8.200%	$247.3236	$247.32	$247.30	$247.30
Purchase #2	$92.47	7.211%	$99.138	$99.14	$99.15	$99.10
Purchase #3	$131.77	11.171%	$146.49	$146.49	$146.50	$146.50
Purchase #4	$215.83	10.189%	$237.8209	$237.82	$237.80	$237.80
Purchase #5	$241.99	5.598%	$255.5366	$255.54	$255.55	$255.50
Purchase #6	$80.35	3.139%	$82.8722	$82.87	$82.85	$82.90
Purchase #7	$235.90	3.808%	$244.8831	$244.88	$244.90	$244.90
7 purchase totals =	$1,226.89		$1,314.0644	$1,314.06	$1,314.05	$1,314.00