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	$59.56	10.137%	$65.5976	$65.60	$65.60	$65.60
Purchase #2	$181.65	12.272%	$203.9421	$203.94	$203.95	$203.90
Purchase #3	$194.48	7.527%	$209.1185	$209.12	$209.10	$209.10
Purchase #4	$59.69	4.716%	$62.505	$62.51	$62.50	$62.50
Purchase #5	$164.66	10.369%	$181.7336	$181.73	$181.75	$181.70
Purchase #6	$146.69	5.613%	$154.9237	$154.92	$154.90	$154.90
Purchase #7	$228.78	5.703%	$241.8273	$241.83	$241.85	$241.80
7 purchase totals =	$1,035.51		$1,119.6478	$1,119.65	$1,119.65	$1,119.50