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	$241.72	8.156%	$261.4347	$261.43	$261.45	$261.40
Purchase #2	$110.88	11.388%	$123.507	$123.51	$123.50	$123.50
Purchase #3	$151.67	9.801%	$166.5352	$166.54	$166.55	$166.50
Purchase #4	$112.93	10.415%	$124.6917	$124.69	$124.70	$124.70
Purchase #5	$153.96	8.257%	$166.6725	$166.67	$166.65	$166.70
Purchase #6	$114.93	7.365%	$123.3946	$123.39	$123.40	$123.40
Purchase #7	$88.83	3.607%	$92.0341	$92.03	$92.05	$92.00
7 purchase totals =	$974.92		$1,058.2698	$1,058.26	$1,058.30	$1,058.20