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	$116.74	11.762%	$130.471	$130.47	$130.45	$130.50
Purchase #2	$105.50	8.546%	$114.516	$114.52	$114.50	$114.50
Purchase #3	$233.51	4.205%	$243.3291	$243.33	$243.35	$243.30
Purchase #4	$74.82	13.720%	$85.0853	$85.09	$85.10	$85.10
Purchase #5	$128.65	6.822%	$137.4265	$137.43	$137.45	$137.40
Purchase #6	$136.85	11.775%	$152.9641	$152.96	$152.95	$153.00
Purchase #7	$200.97	9.338%	$219.7366	$219.74	$219.75	$219.70
7 purchase totals =	$997.04		$1,083.5286	$1,083.54	$1,083.55	$1,083.50