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	$39.87	13.233%	$45.146	$45.15	$45.15	$45.10
Purchase #2	$113.33	12.562%	$127.5665	$127.57	$127.55	$127.60
Purchase #3	$107.35	9.484%	$117.5311	$117.53	$117.55	$117.50
Purchase #4	$113.77	8.536%	$123.4814	$123.48	$123.50	$123.50
Purchase #5	$103.83	8.155%	$112.2973	$112.30	$112.30	$112.30
Purchase #6	$218.98	7.572%	$235.5612	$235.56	$235.55	$235.60
Purchase #7	$23.84	4.556%	$24.9262	$24.93	$24.95	$24.90
7 purchase totals =	$720.97		$786.5097	$786.52	$786.55	$786.50