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	$132.28	13.846%	$150.5955	$150.60	$150.60	$150.60
Purchase #2	$67.61	6.771%	$72.1879	$72.19	$72.20	$72.20
Purchase #3	$229.98	10.279%	$253.6196	$253.62	$253.60	$253.60
Purchase #4	$127.69	7.462%	$137.2182	$137.22	$137.20	$137.20
Purchase #5	$160.42	5.271%	$168.8757	$168.88	$168.90	$168.90
Purchase #6	$107.49	11.192%	$119.5203	$119.52	$119.50	$119.50
Purchase #7	$36.50	6.671%	$38.9349	$38.93	$38.95	$38.90
7 purchase totals =	$861.97		$940.9521	$940.96	$940.95	$940.90