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	$186.51	5.536%	$196.8352	$196.84	$196.85	$196.80
Purchase #2	$208.83	9.704%	$229.0949	$229.09	$229.10	$229.10
Purchase #3	$137.69	10.461%	$152.0938	$152.09	$152.10	$152.10
Purchase #4	$218.97	6.734%	$233.7154	$233.72	$233.70	$233.70
Purchase #5	$235.51	3.662%	$244.1344	$244.13	$244.15	$244.10
Purchase #6	$18.99	12.257%	$21.3176	$21.32	$21.30	$21.30
Purchase #7	$125.80	4.120%	$130.983	$130.98	$131.00	$131.00
7 purchase totals =	$1,132.30		$1,208.1743	$1,208.17	$1,208.20	$1,208.10