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	$139.31	9.135%	$152.036	$152.04	$152.05	$152.00
Purchase #2	$41.33	10.377%	$45.6188	$45.62	$45.60	$45.60
Purchase #3	$215.89	6.804%	$230.5792	$230.58	$230.60	$230.60
Purchase #4	$161.99	11.126%	$180.013	$180.01	$180.00	$180.00
Purchase #5	$12.69	4.758%	$13.2938	$13.29	$13.30	$13.30
Purchase #6	$177.96	5.610%	$187.9436	$187.94	$187.95	$187.90
Purchase #7	$90.25	11.622%	$100.7389	$100.74	$100.75	$100.70
7 purchase totals =	$839.42		$910.2233	$910.22	$910.25	$910.10