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	$82.58	8.472%	$89.5762	$89.58	$89.60	$89.60
Purchase #2	$55.50	4.411%	$57.9481	$57.95	$57.95	$57.90
Purchase #3	$10.82	13.493%	$12.2799	$12.28	$12.30	$12.30
Purchase #4	$142.82	7.340%	$153.303	$153.30	$153.30	$153.30
Purchase #5	$61.38	10.438%	$67.7868	$67.79	$67.80	$67.80
Purchase #6	$50.74	7.665%	$54.6292	$54.63	$54.65	$54.60
Purchase #7	$27.68	8.142%	$29.9337	$29.93	$29.95	$29.90
7 purchase totals =	$431.52		$465.4569	$465.46	$465.55	$465.40