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	$72.35	8.578%	$78.5562	$78.56	$78.55	$78.60
Purchase #2	$174.54	4.545%	$182.4728	$182.47	$182.45	$182.50
Purchase #3	$120.90	3.631%	$125.2899	$125.29	$125.30	$125.30
Purchase #4	$230.81	13.816%	$262.6987	$262.70	$262.70	$262.70
Purchase #5	$24.38	8.848%	$26.5371	$26.54	$26.55	$26.50
Purchase #6	$147.86	3.163%	$152.5368	$152.54	$152.55	$152.50
Purchase #7	$180.30	5.683%	$190.5464	$190.55	$190.55	$190.50
7 purchase totals =	$951.14		$1,018.6379	$1,018.65	$1,018.65	$1,018.60