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	$155.88	7.840%	$168.101	$168.10	$168.10	$168.10
Purchase #2	$199.47	9.221%	$217.8631	$217.86	$217.85	$217.90
Purchase #3	$81.52	11.337%	$90.7619	$90.76	$90.75	$90.80
Purchase #4	$223.41	13.331%	$253.1928	$253.19	$253.20	$253.20
Purchase #5	$246.98	4.404%	$257.857	$257.86	$257.85	$257.90
Purchase #6	$215.68	12.178%	$241.9455	$241.95	$241.95	$241.90
Purchase #7	$182.82	7.622%	$196.7545	$196.75	$196.75	$196.80
7 purchase totals =	$1,305.76		$1,426.4758	$1,426.47	$1,426.45	$1,426.60