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	$103.71	5.692%	$109.6132	$109.61	$109.60	$109.60
Purchase #2	$241.90	4.531%	$252.8605	$252.86	$252.85	$252.90
Purchase #3	$99.79	13.309%	$113.0711	$113.07	$113.05	$113.10
Purchase #4	$123.43	7.601%	$132.8119	$132.81	$132.80	$132.80
Purchase #5	$144.85	7.855%	$156.228	$156.23	$156.25	$156.20
Purchase #6	$180.86	3.127%	$186.5155	$186.52	$186.50	$186.50
Purchase #7	$94.93	12.137%	$106.4517	$106.45	$106.45	$106.50
7 purchase totals =	$989.47		$1,057.5519	$1,057.55	$1,057.50	$1,057.60