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	$123.45	5.473%	$130.2064	$130.21	$130.20	$130.20
Purchase #2	$41.29	9.430%	$45.1836	$45.18	$45.20	$45.20
Purchase #3	$77.38	5.846%	$81.9036	$81.90	$81.90	$81.90
Purchase #4	$162.40	7.311%	$174.2731	$174.27	$174.25	$174.30
Purchase #5	$61.53	8.112%	$66.5213	$66.52	$66.50	$66.50
Purchase #6	$48.95	4.858%	$51.328	$51.33	$51.35	$51.30
Purchase #7	$95.75	10.276%	$105.5893	$105.59	$105.60	$105.60
7 purchase totals =	$610.75		$655.0053	$655.00	$655.00	$655.00