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	$126.59	7.436%	$136.0032	$136.00	$136.00	$136.00
Purchase #2	$101.34	3.612%	$105.0004	$105.00	$105.00	$105.00
Purchase #3	$123.49	4.302%	$128.8025	$128.80	$128.80	$128.80
Purchase #4	$76.32	13.602%	$86.701	$86.70	$86.70	$86.70
Purchase #5	$57.83	11.453%	$64.4533	$64.45	$64.45	$64.50
Purchase #6	$145.66	7.512%	$156.602	$156.60	$156.60	$156.60
Purchase #7	$167.84	10.533%	$185.5186	$185.52	$185.50	$185.50
7 purchase totals =	$799.07		$863.0810	$863.07	$863.05	$863.10