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	$74.55	4.863%	$78.1754	$78.18	$78.20	$78.20
Purchase #2	$248.76	3.189%	$256.693	$256.69	$256.70	$256.70
Purchase #3	$211.54	4.863%	$221.8272	$221.83	$221.85	$221.80
Purchase #4	$137.59	12.760%	$155.1465	$155.15	$155.15	$155.10
Purchase #5	$202.98	12.189%	$227.7212	$227.72	$227.70	$227.70
Purchase #6	$101.75	10.855%	$112.795	$112.80	$112.80	$112.80
Purchase #7	$124.58	10.247%	$137.3457	$137.35	$137.35	$137.30
7 purchase totals =	$1,101.75		$1,189.7040	$1,189.72	$1,189.75	$1,189.60