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	$211.85	7.487%	$227.7112	$227.71	$227.70	$227.70
Purchase #2	$78.81	3.783%	$81.7914	$81.79	$81.80	$81.80
Purchase #3	$131.85	9.654%	$144.5788	$144.58	$144.60	$144.60
Purchase #4	$250.25	7.434%	$268.8536	$268.85	$268.85	$268.90
Purchase #5	$67.95	9.655%	$74.5106	$74.51	$74.50	$74.50
Purchase #6	$238.83	7.371%	$256.4342	$256.43	$256.45	$256.40
Purchase #7	$92.71	12.821%	$104.5963	$104.60	$104.60	$104.60
7 purchase totals =	$1,072.25		$1,158.4761	$1,158.47	$1,158.50	$1,158.50