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	$154.63	5.834%	$163.6511	$163.65	$163.65	$163.70
Purchase #2	$187.39	6.771%	$200.0782	$200.08	$200.10	$200.10
Purchase #3	$57.89	3.251%	$59.772	$59.77	$59.75	$59.80
Purchase #4	$55.25	7.754%	$59.5341	$59.53	$59.55	$59.50
Purchase #5	$103.42	4.684%	$108.2642	$108.26	$108.25	$108.30
Purchase #6	$250.26	11.853%	$279.9233	$279.92	$279.90	$279.90
Purchase #7	$62.58	11.535%	$69.7986	$69.80	$69.80	$69.80
7 purchase totals =	$871.42		$941.0215	$941.01	$941.00	$941.10