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	$57.32	3.172%	$59.1382	$59.14	$59.15	$59.10
Purchase #2	$128.59	13.202%	$145.5665	$145.57	$145.55	$145.60
Purchase #3	$241.55	6.386%	$256.9754	$256.98	$257.00	$257.00
Purchase #4	$249.73	5.293%	$262.9482	$262.95	$262.95	$262.90
Purchase #5	$147.85	3.369%	$152.8311	$152.83	$152.85	$152.80
Purchase #6	$184.95	8.447%	$200.5727	$200.57	$200.55	$200.60
Purchase #7	$219.53	10.451%	$242.4731	$242.47	$242.45	$242.50
7 purchase totals =	$1,229.52		$1,320.5052	$1,320.51	$1,320.50	$1,320.50