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	$202.29	6.565%	$215.5703	$215.57	$215.55	$215.60
Purchase #2	$52.69	13.738%	$59.9286	$59.93	$59.95	$59.90
Purchase #3	$142.85	8.788%	$155.4037	$155.40	$155.40	$155.40
Purchase #4	$142.69	6.451%	$151.8949	$151.89	$151.90	$151.90
Purchase #5	$118.67	7.798%	$127.9239	$127.92	$127.90	$127.90
Purchase #6	$106.74	9.797%	$117.1973	$117.20	$117.20	$117.20
Purchase #7	$13.36	4.873%	$14.011	$14.01	$14.00	$14.00
7 purchase totals =	$779.29		$841.9297	$841.92	$841.90	$841.90