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	$71.45	5.789%	$75.5862	$75.59	$75.60	$75.60
Purchase #2	$74.54	5.123%	$78.3587	$78.36	$78.35	$78.40
Purchase #3	$66.41	8.118%	$71.8012	$71.80	$71.80	$71.80
Purchase #4	$36.64	3.240%	$37.8271	$37.83	$37.85	$37.80
Purchase #5	$25.82	4.357%	$26.945	$26.95	$26.95	$26.90
Purchase #6	$168.97	13.778%	$192.2507	$192.25	$192.25	$192.30
Purchase #7	$103.34	8.316%	$111.9338	$111.93	$111.95	$111.90
7 purchase totals =	$547.17		$594.7027	$594.71	$594.75	$594.70