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	$30.29	7.623%	$32.599	$32.60	$32.60	$32.60
Purchase #2	$50.92	8.805%	$55.4035	$55.40	$55.40	$55.40
Purchase #3	$23.86	6.452%	$25.3994	$25.40	$25.40	$25.40
Purchase #4	$22.51	12.143%	$25.2434	$25.24	$25.25	$25.20
Purchase #5	$204.65	5.800%	$216.5197	$216.52	$216.50	$216.50
Purchase #6	$160.58	7.427%	$172.5063	$172.51	$172.50	$172.50
Purchase #7	$220.60	4.763%	$231.1072	$231.11	$231.10	$231.10
7 purchase totals =	$713.41		$758.7785	$758.78	$758.75	$758.70