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	$57.82	7.694%	$62.2687	$62.27	$62.25	$62.30
Purchase #2	$62.71	5.596%	$66.2193	$66.22	$66.20	$66.20
Purchase #3	$220.75	12.727%	$248.8449	$248.84	$248.85	$248.80
Purchase #4	$162.59	7.599%	$174.9452	$174.95	$174.95	$174.90
Purchase #5	$113.85	8.793%	$123.8608	$123.86	$123.85	$123.90
Purchase #6	$60.82	9.570%	$66.6405	$66.64	$66.65	$66.60
Purchase #7	$117.71	4.573%	$123.0929	$123.09	$123.10	$123.10
7 purchase totals =	$796.25		$865.8723	$865.87	$865.85	$865.80