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	$206.55	3.176%	$213.11	$213.11	$213.10	$213.10
Purchase #2	$101.30	11.287%	$112.7337	$112.73	$112.75	$112.70
Purchase #3	$38.42	13.225%	$43.501	$43.50	$43.50	$43.50
Purchase #4	$45.35	11.253%	$50.4532	$50.45	$50.45	$50.50
Purchase #5	$203.97	5.603%	$215.3984	$215.40	$215.40	$215.40
Purchase #6	$106.86	4.795%	$111.9839	$111.98	$112.00	$112.00
Purchase #7	$162.98	10.639%	$180.3194	$180.32	$180.30	$180.30
7 purchase totals =	$865.43		$927.4996	$927.49	$927.50	$927.50