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	$23.37	12.108%	$26.1996	$26.20	$26.20	$26.20
Purchase #2	$64.43	11.787%	$72.0244	$72.02	$72.00	$72.00
Purchase #3	$121.49	10.799%	$134.6097	$134.61	$134.60	$134.60
Purchase #4	$33.44	11.292%	$37.216	$37.22	$37.20	$37.20
Purchase #5	$172.88	3.636%	$179.1659	$179.17	$179.15	$179.20
Purchase #6	$230.54	10.856%	$255.5674	$255.57	$255.55	$255.60
Purchase #7	$154.57	6.187%	$164.1332	$164.13	$164.15	$164.10
7 purchase totals =	$800.72		$868.9162	$868.92	$868.85	$868.90