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	$151.51	9.552%	$165.9822	$165.98	$166.00	$166.00
Purchase #2	$67.29	9.618%	$73.762	$73.76	$73.75	$73.80
Purchase #3	$127.71	10.350%	$140.928	$140.93	$140.95	$140.90
Purchase #4	$216.57	9.388%	$236.9016	$236.90	$236.90	$236.90
Purchase #5	$8.76	12.431%	$9.849	$9.85	$9.85	$9.80
Purchase #6	$85.78	5.524%	$90.5185	$90.52	$90.50	$90.50
Purchase #7	$167.32	13.561%	$190.0103	$190.01	$190.00	$190.00
7 purchase totals =	$824.94		$907.9516	$907.95	$907.95	$907.90