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	$63.64	3.637%	$65.9546	$65.95	$65.95	$66.00
Purchase #2	$172.55	6.861%	$184.3887	$184.39	$184.40	$184.40
Purchase #3	$40.52	11.121%	$45.0262	$45.03	$45.05	$45.00
Purchase #4	$104.55	4.322%	$109.0687	$109.07	$109.05	$109.10
Purchase #5	$33.80	13.624%	$38.4049	$38.40	$38.40	$38.40
Purchase #6	$104.50	3.208%	$107.8524	$107.85	$107.85	$107.90
Purchase #7	$129.52	11.295%	$144.1493	$144.15	$144.15	$144.10
7 purchase totals =	$649.08		$694.8448	$694.84	$694.85	$694.90