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	$11.86	4.538%	$12.3982	$12.40	$12.40	$12.40
Purchase #2	$48.29	10.296%	$53.2619	$53.26	$53.25	$53.30
Purchase #3	$90.85	12.719%	$102.4052	$102.41	$102.40	$102.40
Purchase #4	$76.58	12.468%	$86.128	$86.13	$86.15	$86.10
Purchase #5	$151.63	6.826%	$161.9803	$161.98	$162.00	$162.00
Purchase #6	$77.91	4.579%	$81.4775	$81.48	$81.50	$81.50
Purchase #7	$173.71	3.713%	$180.1599	$180.16	$180.15	$180.20
7 purchase totals =	$630.83		$677.8110	$677.82	$677.85	$677.90