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	$112.36	3.708%	$116.5263	$116.53	$116.55	$116.50
Purchase #2	$57.80	8.699%	$62.828	$62.83	$62.85	$62.80
Purchase #3	$86.59	4.140%	$90.1748	$90.17	$90.15	$90.20
Purchase #4	$41.41	11.509%	$46.1759	$46.18	$46.20	$46.20
Purchase #5	$155.52	6.421%	$165.5059	$165.51	$165.50	$165.50
Purchase #6	$17.35	4.686%	$18.163	$18.16	$18.15	$18.20
Purchase #7	$47.30	10.686%	$52.3545	$52.35	$52.35	$52.40
7 purchase totals =	$518.33		$551.7284	$551.73	$551.75	$551.80