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	$82.94	4.227%	$86.4459	$86.45	$86.45	$86.40
Purchase #2	$155.46	7.639%	$167.3356	$167.34	$167.35	$167.30
Purchase #3	$113.57	6.826%	$121.3223	$121.32	$121.30	$121.30
Purchase #4	$217.36	7.554%	$233.7794	$233.78	$233.80	$233.80
Purchase #5	$132.81	9.203%	$145.0325	$145.03	$145.05	$145.00
Purchase #6	$80.62	10.489%	$89.0762	$89.08	$89.10	$89.10
Purchase #7	$127.43	5.565%	$134.5215	$134.52	$134.50	$134.50
7 purchase totals =	$910.19		$977.5134	$977.52	$977.55	$977.40