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	$171.79	13.382%	$194.7789	$194.78	$194.80	$194.80
Purchase #2	$171.47	4.147%	$178.5809	$178.58	$178.60	$178.60
Purchase #3	$83.32	3.841%	$86.5203	$86.52	$86.50	$86.50
Purchase #4	$139.91	3.511%	$144.8222	$144.82	$144.80	$144.80
Purchase #5	$50.63	8.627%	$54.9979	$55.00	$55.00	$55.00
Purchase #6	$167.29	10.372%	$184.6413	$184.64	$184.65	$184.60
Purchase #7	$126.47	3.827%	$131.31	$131.31	$131.30	$131.30
7 purchase totals =	$910.88		$975.6515	$975.65	$975.65	$975.60