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	$65.96	10.618%	$72.9636	$72.96	$72.95	$73.00
Purchase #2	$77.38	12.799%	$87.2839	$87.28	$87.30	$87.30
Purchase #3	$197.39	5.789%	$208.8169	$208.82	$208.80	$208.80
Purchase #4	$131.89	13.756%	$150.0328	$150.03	$150.05	$150.00
Purchase #5	$124.47	3.314%	$128.5949	$128.59	$128.60	$128.60
Purchase #6	$244.92	8.658%	$266.1252	$266.13	$266.15	$266.10
Purchase #7	$229.91	3.379%	$237.6787	$237.68	$237.70	$237.70
7 purchase totals =	$1,071.92		$1,151.4960	$1,151.49	$1,151.55	$1,151.50