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	$137.77	13.365%	$156.183	$156.18	$156.20	$156.20
Purchase #2	$184.78	6.452%	$196.702	$196.70	$196.70	$196.70
Purchase #3	$34.84	12.225%	$39.0992	$39.10	$39.10	$39.10
Purchase #4	$24.43	3.697%	$25.3332	$25.33	$25.35	$25.30
Purchase #5	$191.71	4.771%	$200.8565	$200.86	$200.85	$200.90
Purchase #6	$111.85	10.157%	$123.2106	$123.21	$123.20	$123.20
Purchase #7	$42.94	8.259%	$46.4864	$46.49	$46.50	$46.50
7 purchase totals =	$728.32		$787.8709	$787.87	$787.90	$787.90