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	$91.60	12.253%	$102.8237	$102.82	$102.80	$102.80
Purchase #2	$210.68	8.142%	$227.8336	$227.83	$227.85	$227.80
Purchase #3	$89.80	4.854%	$94.1589	$94.16	$94.15	$94.20
Purchase #4	$210.38	13.150%	$238.045	$238.05	$238.05	$238.00
Purchase #5	$141.49	5.139%	$148.7612	$148.76	$148.75	$148.80
Purchase #6	$91.51	4.103%	$95.2647	$95.26	$95.25	$95.30
Purchase #7	$233.39	7.291%	$250.4065	$250.41	$250.40	$250.40
7 purchase totals =	$1,068.85		$1,157.2936	$1,157.29	$1,157.25	$1,157.30