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	$24.37	4.310%	$25.4203	$25.42	$25.40	$25.40
Purchase #2	$158.39	10.315%	$174.7279	$174.73	$174.75	$174.70
Purchase #3	$77.60	13.615%	$88.1652	$88.17	$88.15	$88.20
Purchase #4	$152.96	5.205%	$160.9216	$160.92	$160.90	$160.90
Purchase #5	$244.76	5.145%	$257.3529	$257.35	$257.35	$257.40
Purchase #6	$95.67	3.575%	$99.0902	$99.09	$99.10	$99.10
Purchase #7	$154.40	11.709%	$172.4787	$172.48	$172.50	$172.50
7 purchase totals =	$908.15		$978.1568	$978.16	$978.15	$978.20