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	$136.41	3.812%	$141.6099	$141.61	$141.60	$141.60
Purchase #2	$121.46	4.425%	$126.8346	$126.83	$126.85	$126.80
Purchase #3	$88.59	8.150%	$95.8101	$95.81	$95.80	$95.80
Purchase #4	$104.27	8.693%	$113.3342	$113.33	$113.35	$113.30
Purchase #5	$210.44	5.771%	$222.5845	$222.58	$222.60	$222.60
Purchase #6	$102.96	4.496%	$107.5891	$107.59	$107.60	$107.60
Purchase #7	$177.54	9.462%	$194.3388	$194.34	$194.35	$194.30
7 purchase totals =	$941.67		$1,002.1012	$1,002.09	$1,002.15	$1,002.00