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	$38.72	3.671%	$40.1414	$40.14	$40.15	$40.10
Purchase #2	$141.48	8.513%	$153.5242	$153.52	$153.50	$153.50
Purchase #3	$12.81	12.228%	$14.3764	$14.38	$14.40	$14.40
Purchase #4	$131.45	9.249%	$143.6078	$143.61	$143.60	$143.60
Purchase #5	$201.64	5.360%	$212.4479	$212.45	$212.45	$212.40
Purchase #6	$250.60	10.103%	$275.9181	$275.92	$275.90	$275.90
Purchase #7	$169.78	7.284%	$182.1468	$182.15	$182.15	$182.10
7 purchase totals =	$946.48		$1,022.1626	$1,022.17	$1,022.15	$1,022.00