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	$119.60	12.500%	$134.55	$134.55	$134.55	$134.60
Purchase #2	$134.59	7.213%	$144.298	$144.30	$144.30	$144.30
Purchase #3	$72.83	4.302%	$75.9631	$75.96	$75.95	$76.00
Purchase #4	$69.44	12.166%	$77.8881	$77.89	$77.90	$77.90
Purchase #5	$233.77	12.229%	$262.3577	$262.36	$262.35	$262.40
Purchase #6	$105.45	6.702%	$112.5173	$112.52	$112.50	$112.50
Purchase #7	$57.89	3.548%	$59.9439	$59.94	$59.95	$59.90
7 purchase totals =	$793.57		$867.5181	$867.52	$867.50	$867.60