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	$145.79	7.611%	$156.8861	$156.89	$156.90	$156.90
Purchase #2	$202.85	3.726%	$210.4082	$210.41	$210.40	$210.40
Purchase #3	$67.66	6.555%	$72.0951	$72.10	$72.10	$72.10
Purchase #4	$163.77	12.866%	$184.8406	$184.84	$184.85	$184.80
Purchase #5	$23.58	4.246%	$24.5812	$24.58	$24.60	$24.60
Purchase #6	$176.43	13.693%	$200.5886	$200.59	$200.60	$200.60
Purchase #7	$221.28	13.447%	$251.0355	$251.04	$251.05	$251.00
7 purchase totals =	$1,001.36		$1,100.4353	$1,100.45	$1,100.50	$1,100.40