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	$169.40	10.872%	$187.8172	$187.82	$187.80	$187.80
Purchase #2	$172.86	10.857%	$191.6274	$191.63	$191.65	$191.60
Purchase #3	$164.57	5.629%	$173.8336	$173.83	$173.85	$173.80
Purchase #4	$240.82	6.292%	$255.9724	$255.97	$255.95	$256.00
Purchase #5	$95.45	6.400%	$101.5588	$101.56	$101.55	$101.60
Purchase #6	$142.65	5.612%	$150.6555	$150.66	$150.65	$150.70
Purchase #7	$32.32	10.626%	$35.7543	$35.75	$35.75	$35.80
7 purchase totals =	$1,018.07		$1,097.2192	$1,097.22	$1,097.20	$1,097.30