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	$167.91	7.164%	$179.9391	$179.94	$179.95	$179.90
Purchase #2	$9.85	8.204%	$10.6581	$10.66	$10.65	$10.70
Purchase #3	$26.87	10.325%	$29.6443	$29.64	$29.65	$29.60
Purchase #4	$119.53	12.866%	$134.9087	$134.91	$134.90	$134.90
Purchase #5	$110.96	11.299%	$123.4974	$123.50	$123.50	$123.50
Purchase #6	$131.52	3.657%	$136.3297	$136.33	$136.35	$136.30
Purchase #7	$163.73	13.312%	$185.5257	$185.53	$185.55	$185.50
7 purchase totals =	$730.37		$800.5030	$800.51	$800.55	$800.40