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	$218.89	9.133%	$238.8812	$238.88	$238.90	$238.90
Purchase #2	$79.72	3.294%	$82.346	$82.35	$82.35	$82.30
Purchase #3	$52.61	4.792%	$55.1311	$55.13	$55.15	$55.10
Purchase #4	$154.52	13.392%	$175.2133	$175.21	$175.20	$175.20
Purchase #5	$138.42	13.849%	$157.5898	$157.59	$157.60	$157.60
Purchase #6	$194.61	4.667%	$203.6924	$203.69	$203.70	$203.70
Purchase #7	$104.94	5.172%	$110.3675	$110.37	$110.35	$110.40
7 purchase totals =	$943.71		$1,023.2213	$1,023.22	$1,023.25	$1,023.20