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	$105.47	7.141%	$113.0016	$113.00	$113.00	$113.00
Purchase #2	$107.87	4.187%	$112.3865	$112.39	$112.40	$112.40
Purchase #3	$24.60	12.141%	$27.5867	$27.59	$27.60	$27.60
Purchase #4	$58.88	8.232%	$63.727	$63.73	$63.75	$63.70
Purchase #5	$50.89	7.133%	$54.52	$54.52	$54.50	$54.50
Purchase #6	$96.82	4.144%	$100.8322	$100.83	$100.85	$100.80
Purchase #7	$135.53	13.189%	$153.4051	$153.41	$153.40	$153.40
7 purchase totals =	$580.06		$625.4591	$625.47	$625.50	$625.40