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	$98.94	12.636%	$111.4421	$111.44	$111.45	$111.40
Purchase #2	$140.72	7.143%	$150.7716	$150.77	$150.75	$150.80
Purchase #3	$178.87	8.816%	$194.6392	$194.64	$194.65	$194.60
Purchase #4	$82.27	11.163%	$91.4538	$91.45	$91.45	$91.50
Purchase #5	$41.67	6.719%	$44.4698	$44.47	$44.45	$44.50
Purchase #6	$239.25	8.647%	$259.9379	$259.94	$259.95	$259.90
Purchase #7	$56.75	9.724%	$62.2684	$62.27	$62.25	$62.30
7 purchase totals =	$838.47		$914.9828	$914.98	$914.95	$915.00