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	$140.65	4.581%	$147.0932	$147.09	$147.10	$147.10
Purchase #2	$227.59	5.624%	$240.3897	$240.39	$240.40	$240.40
Purchase #3	$103.60	7.760%	$111.6394	$111.64	$111.65	$111.60
Purchase #4	$222.85	9.427%	$243.8581	$243.86	$243.85	$243.90
Purchase #5	$63.94	12.763%	$72.1007	$72.10	$72.10	$72.10
Purchase #6	$138.45	5.347%	$145.8529	$145.85	$145.85	$145.90
Purchase #7	$118.66	3.548%	$122.8701	$122.87	$122.85	$122.90
7 purchase totals =	$1,015.74		$1,083.8041	$1,083.80	$1,083.80	$1,083.90