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	$74.35	11.496%	$82.8973	$82.90	$82.90	$82.90
Purchase #2	$49.85	9.639%	$54.655	$54.66	$54.65	$54.70
Purchase #3	$36.32	4.134%	$37.8215	$37.82	$37.80	$37.80
Purchase #4	$132.50	3.849%	$137.5999	$137.60	$137.60	$137.60
Purchase #5	$48.40	9.461%	$52.9791	$52.98	$53.00	$53.00
Purchase #6	$96.73	4.241%	$100.8323	$100.83	$100.85	$100.80
Purchase #7	$143.29	9.718%	$157.2149	$157.21	$157.20	$157.20
7 purchase totals =	$581.44		$624.0000	$624.00	$624.00	$624.00