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	$74.89	9.807%	$82.2345	$82.23	$82.25	$82.20
Purchase #2	$70.27	3.345%	$72.6205	$72.62	$72.60	$72.60
Purchase #3	$97.74	7.191%	$104.7685	$104.77	$104.75	$104.80
Purchase #4	$194.45	11.834%	$217.4612	$217.46	$217.45	$217.50
Purchase #5	$81.64	7.720%	$87.9426	$87.94	$87.95	$87.90
Purchase #6	$103.99	13.408%	$117.933	$117.93	$117.95	$117.90
Purchase #7	$144.71	12.568%	$162.8972	$162.90	$162.90	$162.90
7 purchase totals =	$767.69		$845.8575	$845.85	$845.85	$845.80