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	$86.27	7.247%	$92.522	$92.52	$92.50	$92.50
Purchase #2	$54.43	9.602%	$59.6564	$59.66	$59.65	$59.70
Purchase #3	$241.69	9.371%	$264.3388	$264.34	$264.35	$264.30
Purchase #4	$118.80	5.699%	$125.5704	$125.57	$125.55	$125.60
Purchase #5	$29.55	10.819%	$32.747	$32.75	$32.75	$32.70
Purchase #6	$116.73	8.383%	$126.5155	$126.52	$126.50	$126.50
Purchase #7	$153.89	5.610%	$162.5232	$162.52	$162.50	$162.50
7 purchase totals =	$801.36		$863.8733	$863.88	$863.80	$863.80