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	$193.39	6.828%	$206.5947	$206.59	$206.60	$206.60
Purchase #2	$67.98	6.624%	$72.483	$72.48	$72.50	$72.50
Purchase #3	$240.98	4.260%	$251.2457	$251.25	$251.25	$251.20
Purchase #4	$167.66	3.406%	$173.3705	$173.37	$173.35	$173.40
Purchase #5	$57.68	4.261%	$60.1377	$60.14	$60.15	$60.10
Purchase #6	$238.59	6.638%	$254.4276	$254.43	$254.45	$254.40
Purchase #7	$118.43	7.655%	$127.4958	$127.50	$127.50	$127.50
7 purchase totals =	$1,084.71		$1,145.7550	$1,145.76	$1,145.80	$1,145.70