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	$124.93	3.112%	$128.8178	$128.82	$128.80	$128.80
Purchase #2	$44.36	3.478%	$45.9028	$45.90	$45.90	$45.90
Purchase #3	$34.49	7.531%	$37.0874	$37.09	$37.10	$37.10
Purchase #4	$100.77	10.371%	$111.2209	$111.22	$111.20	$111.20
Purchase #5	$122.35	10.189%	$134.8162	$134.82	$134.80	$134.80
Purchase #6	$53.67	10.157%	$59.1213	$59.12	$59.10	$59.10
Purchase #7	$172.37	5.460%	$181.7814	$181.78	$181.80	$181.80
7 purchase totals =	$652.94		$698.7478	$698.75	$698.70	$698.70