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	$220.98	3.107%	$227.8458	$227.85	$227.85	$227.80
Purchase #2	$153.60	7.277%	$164.7775	$164.78	$164.80	$164.80
Purchase #3	$205.39	9.720%	$225.3539	$225.35	$225.35	$225.40
Purchase #4	$64.40	3.864%	$66.8884	$66.89	$66.90	$66.90
Purchase #5	$165.82	13.677%	$188.4992	$188.50	$188.50	$188.50
Purchase #6	$205.35	9.212%	$224.2668	$224.27	$224.25	$224.30
Purchase #7	$146.31	12.408%	$164.4641	$164.46	$164.45	$164.50
7 purchase totals =	$1,161.85		$1,262.0957	$1,262.10	$1,262.10	$1,262.20