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	$58.28	6.136%	$61.8561	$61.86	$61.85	$61.90
Purchase #2	$165.93	6.290%	$176.367	$176.37	$176.35	$176.40
Purchase #3	$230.77	6.715%	$246.2662	$246.27	$246.25	$246.30
Purchase #4	$83.65	8.570%	$90.8188	$90.82	$90.80	$90.80
Purchase #5	$55.33	5.284%	$58.2536	$58.25	$58.25	$58.30
Purchase #6	$39.28	10.617%	$43.4504	$43.45	$43.45	$43.50
Purchase #7	$196.47	11.737%	$219.5297	$219.53	$219.55	$219.50
7 purchase totals =	$829.71		$896.5418	$896.55	$896.50	$896.70