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	$109.40	7.551%	$117.6608	$117.66	$117.65	$117.70
Purchase #2	$174.87	12.504%	$196.7357	$196.74	$196.75	$196.70
Purchase #3	$231.92	6.868%	$247.8483	$247.85	$247.85	$247.80
Purchase #4	$61.45	7.120%	$65.8252	$65.83	$65.85	$65.80
Purchase #5	$134.90	5.167%	$141.8703	$141.87	$141.85	$141.90
Purchase #6	$183.68	13.675%	$208.7982	$208.80	$208.80	$208.80
Purchase #7	$120.30	8.832%	$130.9249	$130.92	$130.90	$130.90
7 purchase totals =	$1,016.52		$1,109.6634	$1,109.67	$1,109.65	$1,109.60