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	$178.67	10.135%	$196.7782	$196.78	$196.80	$196.80
Purchase #2	$182.58	12.806%	$205.9612	$205.96	$205.95	$206.00
Purchase #3	$172.94	10.501%	$191.1004	$191.10	$191.10	$191.10
Purchase #4	$142.57	8.480%	$154.6599	$154.66	$154.65	$154.70
Purchase #5	$51.67	6.295%	$54.9226	$54.92	$54.90	$54.90
Purchase #6	$67.64	7.687%	$72.8395	$72.84	$72.85	$72.80
Purchase #7	$181.87	12.488%	$204.5819	$204.58	$204.60	$204.60
7 purchase totals =	$977.94		$1,080.8437	$1,080.84	$1,080.85	$1,080.90