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	$123.36	7.680%	$132.834	$132.83	$132.85	$132.80
Purchase #2	$9.53	8.188%	$10.3103	$10.31	$10.30	$10.30
Purchase #3	$210.45	3.204%	$217.1928	$217.19	$217.20	$217.20
Purchase #4	$117.58	8.272%	$127.3062	$127.31	$127.30	$127.30
Purchase #5	$59.38	4.112%	$61.8217	$61.82	$61.80	$61.80
Purchase #6	$179.85	12.324%	$202.0147	$202.01	$202.00	$202.00
Purchase #7	$29.30	6.252%	$31.1318	$31.13	$31.15	$31.10
7 purchase totals =	$729.45		$782.6115	$782.60	$782.60	$782.50