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	$242.53	5.210%	$255.1658	$255.17	$255.15	$255.20
Purchase #2	$88.36	13.151%	$99.9802	$99.98	$100.00	$100.00
Purchase #3	$212.99	13.198%	$241.1004	$241.10	$241.10	$241.10
Purchase #4	$34.73	5.126%	$36.5103	$36.51	$36.50	$36.50
Purchase #5	$245.67	5.806%	$259.9336	$259.93	$259.95	$259.90
Purchase #6	$43.52	4.284%	$45.3844	$45.38	$45.40	$45.40
Purchase #7	$139.38	5.574%	$147.149	$147.15	$147.15	$147.10
7 purchase totals =	$1,007.18		$1,085.2237	$1,085.22	$1,085.25	$1,085.20