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	$105.80	9.426%	$115.7727	$115.77	$115.75	$115.80
Purchase #2	$182.66	7.496%	$196.3522	$196.35	$196.35	$196.40
Purchase #3	$139.59	3.413%	$144.3542	$144.35	$144.35	$144.40
Purchase #4	$215.90	5.734%	$228.2797	$228.28	$228.30	$228.30
Purchase #5	$250.74	3.483%	$259.4733	$259.47	$259.45	$259.50
Purchase #6	$230.41	5.103%	$242.1678	$242.17	$242.15	$242.20
Purchase #7	$161.89	9.265%	$176.8891	$176.89	$176.90	$176.90
7 purchase totals =	$1,286.99		$1,363.2890	$1,363.28	$1,363.25	$1,363.50