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	$186.50	9.620%	$204.4413	$204.44	$204.45	$204.40
Purchase #2	$212.87	10.106%	$234.3826	$234.38	$234.40	$234.40
Purchase #3	$239.69	5.271%	$252.3241	$252.32	$252.30	$252.30
Purchase #4	$128.47	9.579%	$140.7761	$140.78	$140.80	$140.80
Purchase #5	$62.79	6.422%	$66.8224	$66.82	$66.80	$66.80
Purchase #6	$53.31	11.134%	$59.2455	$59.25	$59.25	$59.20
Purchase #7	$143.99	6.636%	$153.5452	$153.55	$153.55	$153.50
7 purchase totals =	$1,027.62		$1,111.5372	$1,111.54	$1,111.55	$1,111.40