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	$79.75	12.303%	$89.5616	$89.56	$89.55	$89.60
Purchase #2	$18.40	11.457%	$20.5081	$20.51	$20.50	$20.50
Purchase #3	$40.92	10.622%	$45.2665	$45.27	$45.25	$45.30
Purchase #4	$94.70	9.254%	$103.4635	$103.46	$103.45	$103.50
Purchase #5	$235.66	3.797%	$244.608	$244.61	$244.60	$244.60
Purchase #6	$146.96	5.202%	$154.6049	$154.60	$154.60	$154.60
Purchase #7	$101.43	3.469%	$104.9486	$104.95	$104.95	$104.90
7 purchase totals =	$717.82		$762.9612	$762.96	$762.90	$763.00