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	$52.51	12.685%	$59.1709	$59.17	$59.15	$59.20
Purchase #2	$166.67	9.552%	$182.5903	$182.59	$182.60	$182.60
Purchase #3	$176.32	9.164%	$192.478	$192.48	$192.50	$192.50
Purchase #4	$236.63	10.363%	$261.152	$261.15	$261.15	$261.20
Purchase #5	$40.47	5.610%	$42.7404	$42.74	$42.75	$42.70
Purchase #6	$230.77	12.133%	$258.7693	$258.77	$258.75	$258.80
Purchase #7	$235.75	8.676%	$256.2037	$256.20	$256.20	$256.20
7 purchase totals =	$1,139.12		$1,253.1046	$1,253.10	$1,253.10	$1,253.20