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	$116.73	10.466%	$128.947	$128.95	$128.95	$128.90
Purchase #2	$47.32	3.134%	$48.803	$48.80	$48.80	$48.80
Purchase #3	$145.96	13.704%	$165.9624	$165.96	$165.95	$166.00
Purchase #4	$139.32	13.482%	$158.1031	$158.10	$158.10	$158.10
Purchase #5	$133.83	3.706%	$138.7897	$138.79	$138.80	$138.80
Purchase #6	$204.58	11.333%	$227.7651	$227.77	$227.75	$227.80
Purchase #7	$240.94	13.506%	$273.4814	$273.48	$273.50	$273.50
7 purchase totals =	$1,028.68		$1,141.8517	$1,141.85	$1,141.85	$1,141.90