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	$230.58	7.538%	$247.9611	$247.96	$247.95	$248.00
Purchase #2	$30.91	3.165%	$31.8883	$31.89	$31.90	$31.90
Purchase #3	$33.79	5.326%	$35.5897	$35.59	$35.60	$35.60
Purchase #4	$17.25	6.182%	$18.3164	$18.32	$18.30	$18.30
Purchase #5	$76.42	13.739%	$86.9193	$86.92	$86.90	$86.90
Purchase #6	$192.66	13.705%	$219.0641	$219.06	$219.05	$219.10
Purchase #7	$238.89	13.379%	$270.8511	$270.85	$270.85	$270.90
7 purchase totals =	$820.50		$910.5900	$910.59	$910.55	$910.70