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	$205.45	11.174%	$228.407	$228.41	$228.40	$228.40
Purchase #2	$37.33	10.857%	$41.3829	$41.38	$41.40	$41.40
Purchase #3	$105.86	10.855%	$117.3511	$117.35	$117.35	$117.40
Purchase #4	$247.65	5.583%	$261.4763	$261.48	$261.50	$261.50
Purchase #5	$52.77	12.400%	$59.3135	$59.31	$59.30	$59.30
Purchase #6	$137.92	12.278%	$154.8538	$154.85	$154.85	$154.90
Purchase #7	$140.93	5.382%	$148.5149	$148.51	$148.50	$148.50
7 purchase totals =	$927.91		$1,011.2995	$1,011.29	$1,011.30	$1,011.40