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	$105.49	6.126%	$111.9523	$111.95	$111.95	$112.00
Purchase #2	$110.92	4.854%	$116.3041	$116.30	$116.30	$116.30
Purchase #3	$72.96	7.575%	$78.4867	$78.49	$78.50	$78.50
Purchase #4	$125.61	12.663%	$141.516	$141.52	$141.50	$141.50
Purchase #5	$142.85	5.392%	$150.5525	$150.55	$150.55	$150.60
Purchase #6	$61.64	7.543%	$66.2895	$66.29	$66.30	$66.30
Purchase #7	$21.47	3.708%	$22.2661	$22.27	$22.25	$22.30
7 purchase totals =	$640.94		$687.3672	$687.37	$687.35	$687.50