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	$185.58	10.212%	$204.5314	$204.53	$204.55	$204.50
Purchase #2	$72.61	9.866%	$79.7737	$79.77	$79.75	$79.80
Purchase #3	$54.86	9.140%	$59.8742	$59.87	$59.85	$59.90
Purchase #4	$67.72	12.867%	$76.4335	$76.43	$76.45	$76.40
Purchase #5	$87.32	3.546%	$90.4164	$90.42	$90.40	$90.40
Purchase #6	$179.71	10.399%	$198.398	$198.40	$198.40	$198.40
Purchase #7	$208.82	5.423%	$220.1443	$220.14	$220.15	$220.10
7 purchase totals =	$856.62		$929.5715	$929.56	$929.55	$929.50