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	$73.99	6.680%	$78.9325	$78.93	$78.95	$78.90
Purchase #2	$52.99	13.177%	$59.9725	$59.97	$59.95	$60.00
Purchase #3	$24.51	11.269%	$27.272	$27.27	$27.25	$27.30
Purchase #4	$97.89	11.168%	$108.8224	$108.82	$108.80	$108.80
Purchase #5	$167.42	12.208%	$187.8586	$187.86	$187.85	$187.90
Purchase #6	$10.31	10.632%	$11.4062	$11.41	$11.40	$11.40
Purchase #7	$234.87	3.106%	$242.1651	$242.17	$242.15	$242.20
7 purchase totals =	$661.98		$716.4293	$716.43	$716.35	$716.50