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	$203.78	5.732%	$215.4607	$215.46	$215.45	$215.50
Purchase #2	$52.59	8.843%	$57.2405	$57.24	$57.25	$57.20
Purchase #3	$96.64	8.163%	$104.5287	$104.53	$104.55	$104.50
Purchase #4	$186.71	9.728%	$204.8731	$204.87	$204.85	$204.90
Purchase #5	$240.90	6.542%	$256.6597	$256.66	$256.65	$256.70
Purchase #6	$199.92	10.778%	$221.4674	$221.47	$221.45	$221.50
Purchase #7	$62.31	7.301%	$66.8593	$66.86	$66.85	$66.90
7 purchase totals =	$1,042.85		$1,127.0894	$1,127.09	$1,127.05	$1,127.20