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	$105.84	5.373%	$111.5268	$111.53	$111.55	$111.50
Purchase #2	$46.95	13.379%	$53.2314	$53.23	$53.25	$53.20
Purchase #3	$126.49	13.400%	$143.4397	$143.44	$143.45	$143.40
Purchase #4	$89.57	6.174%	$95.1001	$95.10	$95.10	$95.10
Purchase #5	$139.67	12.144%	$156.6315	$156.63	$156.65	$156.60
Purchase #6	$135.98	3.321%	$140.4959	$140.50	$140.50	$140.50
Purchase #7	$52.40	5.225%	$55.1379	$55.14	$55.15	$55.10
7 purchase totals =	$696.90		$755.5633	$755.57	$755.65	$755.40