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	$219.58	13.634%	$249.5175	$249.52	$249.50	$249.50
Purchase #2	$227.34	11.390%	$253.234	$253.23	$253.25	$253.20
Purchase #3	$32.42	3.224%	$33.4652	$33.47	$33.45	$33.50
Purchase #4	$149.50	4.679%	$156.4951	$156.50	$156.50	$156.50
Purchase #5	$98.85	13.269%	$111.9664	$111.97	$111.95	$112.00
Purchase #6	$73.90	10.856%	$81.9226	$81.92	$81.90	$81.90
Purchase #7	$53.94	8.545%	$58.5492	$58.55	$58.55	$58.50
7 purchase totals =	$855.53		$945.1500	$945.16	$945.10	$945.10