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	$219.67	12.103%	$246.2567	$246.26	$246.25	$246.30
Purchase #2	$105.73	10.325%	$116.6466	$116.65	$116.65	$116.60
Purchase #3	$193.50	4.699%	$202.5926	$202.59	$202.60	$202.60
Purchase #4	$243.75	9.358%	$266.5601	$266.56	$266.55	$266.60
Purchase #5	$90.89	9.338%	$99.3773	$99.38	$99.40	$99.40
Purchase #6	$161.86	6.247%	$171.9714	$171.97	$171.95	$172.00
Purchase #7	$64.87	11.691%	$72.454	$72.45	$72.45	$72.50
7 purchase totals =	$1,080.27		$1,175.8587	$1,175.86	$1,175.85	$1,176.00