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	$219.37	10.849%	$243.1695	$243.17	$243.15	$243.20
Purchase #2	$16.92	3.453%	$17.5042	$17.50	$17.50	$17.50
Purchase #3	$235.85	5.716%	$249.3312	$249.33	$249.35	$249.30
Purchase #4	$179.83	9.470%	$196.8599	$196.86	$196.85	$196.90
Purchase #5	$59.58	6.578%	$63.4992	$63.50	$63.50	$63.50
Purchase #6	$193.49	7.628%	$208.2494	$208.25	$208.25	$208.20
Purchase #7	$117.84	11.500%	$131.3916	$131.39	$131.40	$131.40
7 purchase totals =	$1,022.88		$1,110.0050	$1,110.00	$1,110.00	$1,110.00