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	$142.85	8.424%	$154.8837	$154.88	$154.90	$154.90
Purchase #2	$104.34	6.560%	$111.1847	$111.18	$111.20	$111.20
Purchase #3	$247.29	7.832%	$266.6578	$266.66	$266.65	$266.70
Purchase #4	$156.30	8.832%	$170.1044	$170.10	$170.10	$170.10
Purchase #5	$41.92	4.621%	$43.8571	$43.86	$43.85	$43.90
Purchase #6	$86.98	4.500%	$90.8941	$90.89	$90.90	$90.90
Purchase #7	$102.90	13.459%	$116.7493	$116.75	$116.75	$116.70
7 purchase totals =	$882.58		$954.3311	$954.32	$954.35	$954.40