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	$151.65	7.362%	$162.8145	$162.81	$162.80	$162.80
Purchase #2	$111.52	12.856%	$125.857	$125.86	$125.85	$125.90
Purchase #3	$80.88	7.657%	$87.073	$87.07	$87.05	$87.10
Purchase #4	$143.61	13.868%	$163.5258	$163.53	$163.55	$163.50
Purchase #5	$151.59	8.397%	$164.319	$164.32	$164.30	$164.30
Purchase #6	$114.49	12.327%	$128.6032	$128.60	$128.60	$128.60
Purchase #7	$72.89	7.716%	$78.5142	$78.51	$78.50	$78.50
7 purchase totals =	$826.63		$910.7067	$910.70	$910.65	$910.70