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	$77.29	4.307%	$80.6189	$80.62	$80.60	$80.60
Purchase #2	$182.69	3.167%	$188.4758	$188.48	$188.50	$188.50
Purchase #3	$56.90	9.392%	$62.244	$62.24	$62.25	$62.20
Purchase #4	$141.95	8.411%	$153.8894	$153.89	$153.90	$153.90
Purchase #5	$174.55	13.762%	$198.5716	$198.57	$198.55	$198.60
Purchase #6	$104.91	7.720%	$113.0091	$113.01	$113.00	$113.00
Purchase #7	$205.40	7.874%	$221.5732	$221.57	$221.55	$221.60
7 purchase totals =	$943.69		$1,018.3820	$1,018.38	$1,018.35	$1,018.40