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	$61.28	6.671%	$65.368	$65.37	$65.35	$65.40
Purchase #2	$142.75	8.196%	$154.4498	$154.45	$154.45	$154.40
Purchase #3	$199.33	10.339%	$219.9387	$219.94	$219.95	$219.90
Purchase #4	$42.99	5.608%	$45.4009	$45.40	$45.40	$45.40
Purchase #5	$157.70	5.556%	$166.4618	$166.46	$166.45	$166.50
Purchase #6	$32.37	9.302%	$35.3811	$35.38	$35.40	$35.40
Purchase #7	$87.78	3.273%	$90.653	$90.65	$90.65	$90.70
7 purchase totals =	$724.20		$777.6533	$777.65	$777.65	$777.70