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	$99.94	13.851%	$113.7827	$113.78	$113.80	$113.80
Purchase #2	$18.27	13.743%	$20.7808	$20.78	$20.80	$20.80
Purchase #3	$158.42	10.329%	$174.7832	$174.78	$174.80	$174.80
Purchase #4	$43.44	7.189%	$46.5629	$46.56	$46.55	$46.60
Purchase #5	$67.60	12.811%	$76.2602	$76.26	$76.25	$76.30
Purchase #6	$53.69	11.667%	$59.954	$59.95	$59.95	$60.00
Purchase #7	$216.85	12.156%	$243.2103	$243.21	$243.20	$243.20
7 purchase totals =	$658.21		$735.3341	$735.32	$735.35	$735.50