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	$104.37	8.553%	$113.2968	$113.30	$113.30	$113.30
Purchase #2	$55.44	6.846%	$59.2354	$59.24	$59.25	$59.20
Purchase #3	$187.49	11.186%	$208.4626	$208.46	$208.45	$208.50
Purchase #4	$189.92	3.383%	$196.345	$196.35	$196.35	$196.30
Purchase #5	$16.68	12.702%	$18.7987	$18.80	$18.80	$18.80
Purchase #6	$122.43	12.135%	$137.2869	$137.29	$137.30	$137.30
Purchase #7	$45.84	11.558%	$51.1382	$51.14	$51.15	$51.10
7 purchase totals =	$722.17		$784.5636	$784.58	$784.60	$784.50