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	$238.46	9.648%	$261.4666	$261.47	$261.45	$261.50
Purchase #2	$241.84	4.391%	$252.4592	$252.46	$252.45	$252.50
Purchase #3	$249.42	9.781%	$273.8158	$273.82	$273.80	$273.80
Purchase #4	$127.48	11.215%	$141.7769	$141.78	$141.80	$141.80
Purchase #5	$64.71	4.380%	$67.5443	$67.54	$67.55	$67.50
Purchase #6	$16.36	13.537%	$18.5747	$18.57	$18.55	$18.60
Purchase #7	$229.43	11.857%	$256.6335	$256.63	$256.65	$256.60
7 purchase totals =	$1,167.70		$1,272.2710	$1,272.27	$1,272.25	$1,272.30