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	$119.36	10.246%	$131.5896	$131.59	$131.60	$131.60
Purchase #2	$19.33	12.470%	$21.7405	$21.74	$21.75	$21.70
Purchase #3	$64.63	3.536%	$66.9153	$66.92	$66.90	$66.90
Purchase #4	$87.92	8.324%	$95.2385	$95.24	$95.25	$95.20
Purchase #5	$137.91	13.417%	$156.4134	$156.41	$156.40	$156.40
Purchase #6	$61.84	9.485%	$67.7055	$67.71	$67.70	$67.70
Purchase #7	$41.38	11.753%	$46.2434	$46.24	$46.25	$46.20
7 purchase totals =	$532.37		$585.8462	$585.85	$585.85	$585.70