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	$221.76	10.448%	$244.9295	$244.93	$244.95	$244.90
Purchase #2	$111.52	7.205%	$119.555	$119.56	$119.55	$119.60
Purchase #3	$39.71	10.527%	$43.8903	$43.89	$43.90	$43.90
Purchase #4	$154.51	12.661%	$174.0725	$174.07	$174.05	$174.10
Purchase #5	$128.95	9.517%	$141.2222	$141.22	$141.20	$141.20
Purchase #6	$65.71	4.406%	$68.6052	$68.61	$68.60	$68.60
Purchase #7	$247.93	9.143%	$270.5982	$270.60	$270.60	$270.60
7 purchase totals =	$970.09		$1,062.8729	$1,062.88	$1,062.85	$1,062.90