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	$208.79	4.494%	$218.173	$218.17	$218.15	$218.20
Purchase #2	$226.86	5.854%	$240.1404	$240.14	$240.15	$240.10
Purchase #3	$72.68	12.571%	$81.8166	$81.82	$81.80	$81.80
Purchase #4	$205.86	4.874%	$215.8936	$215.89	$215.90	$215.90
Purchase #5	$156.78	7.455%	$168.4679	$168.47	$168.45	$168.50
Purchase #6	$153.91	11.839%	$172.1314	$172.13	$172.15	$172.10
Purchase #7	$219.83	4.285%	$229.2497	$229.25	$229.25	$229.20
7 purchase totals =	$1,244.71		$1,325.8726	$1,325.87	$1,325.85	$1,325.80