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	$66.83	10.858%	$74.0864	$74.09	$74.10	$74.10
Purchase #2	$187.88	3.523%	$194.499	$194.50	$194.50	$194.50
Purchase #3	$73.37	3.763%	$76.1309	$76.13	$76.15	$76.10
Purchase #4	$208.84	3.323%	$215.7798	$215.78	$215.80	$215.80
Purchase #5	$32.72	3.730%	$33.9405	$33.94	$33.95	$33.90
Purchase #6	$146.64	4.695%	$153.5247	$153.52	$153.50	$153.50
Purchase #7	$81.89	5.351%	$86.2719	$86.27	$86.25	$86.30
7 purchase totals =	$798.17		$834.2332	$834.23	$834.25	$834.20