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	$239.58	5.500%	$252.7569	$252.76	$252.75	$252.80
Purchase #2	$161.34	7.443%	$173.3485	$173.35	$173.35	$173.30
Purchase #3	$47.26	8.533%	$51.2927	$51.29	$51.30	$51.30
Purchase #4	$95.90	5.238%	$100.9232	$100.92	$100.90	$100.90
Purchase #5	$146.87	12.735%	$165.5739	$165.57	$165.55	$165.60
Purchase #6	$167.78	12.352%	$188.5042	$188.50	$188.50	$188.50
Purchase #7	$123.54	6.513%	$131.5862	$131.59	$131.60	$131.60
7 purchase totals =	$982.27		$1,063.9856	$1,063.98	$1,063.95	$1,064.00