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	$238.72	12.552%	$268.6841	$268.68	$268.70	$268.70
Purchase #2	$84.94	9.830%	$93.2896	$93.29	$93.30	$93.30
Purchase #3	$57.95	13.342%	$65.6817	$65.68	$65.70	$65.70
Purchase #4	$190.52	4.392%	$198.8876	$198.89	$198.90	$198.90
Purchase #5	$216.37	11.301%	$240.822	$240.82	$240.80	$240.80
Purchase #6	$31.46	4.551%	$32.8917	$32.89	$32.90	$32.90
Purchase #7	$56.45	5.711%	$59.6739	$59.67	$59.65	$59.70
7 purchase totals =	$876.41		$959.9306	$959.92	$959.95	$960.00