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	$108.95	13.436%	$123.5885	$123.59	$123.60	$123.60
Purchase #2	$72.82	7.636%	$78.3805	$78.38	$78.40	$78.40
Purchase #3	$53.85	7.794%	$58.0471	$58.05	$58.05	$58.00
Purchase #4	$20.55	4.131%	$21.3989	$21.40	$21.40	$21.40
Purchase #5	$235.92	11.569%	$263.2136	$263.21	$263.20	$263.20
Purchase #6	$93.65	7.758%	$100.9154	$100.92	$100.90	$100.90
Purchase #7	$127.68	11.145%	$141.9099	$141.91	$141.90	$141.90
7 purchase totals =	$713.42		$787.4539	$787.46	$787.45	$787.40