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	$237.60	13.798%	$270.384	$270.38	$270.40	$270.40
Purchase #2	$111.52	13.218%	$126.2607	$126.26	$126.25	$126.30
Purchase #3	$52.66	12.621%	$59.3062	$59.31	$59.30	$59.30
Purchase #4	$154.88	12.616%	$174.4197	$174.42	$174.40	$174.40
Purchase #5	$138.31	5.681%	$146.1674	$146.17	$146.15	$146.20
Purchase #6	$57.94	9.126%	$63.2276	$63.23	$63.25	$63.20
Purchase #7	$177.88	10.242%	$196.0985	$196.10	$196.10	$196.10
7 purchase totals =	$930.79		$1,035.8641	$1,035.87	$1,035.85	$1,035.90