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	$140.54	3.273%	$145.1399	$145.14	$145.15	$145.10
Purchase #2	$136.84	5.405%	$144.2362	$144.24	$144.25	$144.20
Purchase #3	$132.70	7.466%	$142.6074	$142.61	$142.60	$142.60
Purchase #4	$157.57	12.828%	$177.7831	$177.78	$177.80	$177.80
Purchase #5	$90.72	10.729%	$100.4533	$100.45	$100.45	$100.50
Purchase #6	$114.41	8.672%	$124.3316	$124.33	$124.35	$124.30
Purchase #7	$236.74	4.601%	$247.6324	$247.63	$247.65	$247.60
7 purchase totals =	$1,009.52		$1,082.1839	$1,082.18	$1,082.25	$1,082.10