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	$164.85	4.126%	$171.6517	$171.65	$171.65	$171.70
Purchase #2	$38.62	12.358%	$43.3927	$43.39	$43.40	$43.40
Purchase #3	$68.95	13.468%	$78.2362	$78.24	$78.25	$78.20
Purchase #4	$198.51	10.731%	$219.8121	$219.81	$219.80	$219.80
Purchase #5	$151.88	7.582%	$163.3955	$163.40	$163.40	$163.40
Purchase #6	$121.52	4.807%	$127.3615	$127.36	$127.35	$127.40
Purchase #7	$102.56	13.679%	$116.5892	$116.59	$116.60	$116.60
7 purchase totals =	$846.89		$920.4389	$920.44	$920.45	$920.50