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	$183.80	6.733%	$196.1753	$196.18	$196.20	$196.20
Purchase #2	$184.45	11.455%	$205.5787	$205.58	$205.60	$205.60
Purchase #3	$121.95	5.404%	$128.5402	$128.54	$128.55	$128.50
Purchase #4	$169.82	8.733%	$184.6504	$184.65	$184.65	$184.70
Purchase #5	$87.75	11.400%	$97.7535	$97.75	$97.75	$97.80
Purchase #6	$56.51	5.829%	$59.804	$59.80	$59.80	$59.80
Purchase #7	$194.93	9.500%	$213.4484	$213.45	$213.45	$213.40
7 purchase totals =	$999.21		$1,085.9505	$1,085.95	$1,086.00	$1,086.00