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	$229.71	13.732%	$261.2538	$261.25	$261.25	$261.30
Purchase #2	$151.97	3.455%	$157.2206	$157.22	$157.20	$157.20
Purchase #3	$192.45	8.551%	$208.9064	$208.91	$208.90	$208.90
Purchase #4	$114.75	12.219%	$128.7713	$128.77	$128.75	$128.80
Purchase #5	$29.37	6.412%	$31.2532	$31.25	$31.25	$31.30
Purchase #6	$137.42	3.602%	$142.3699	$142.37	$142.35	$142.40
Purchase #7	$131.87	7.359%	$141.5743	$141.57	$141.55	$141.60
7 purchase totals =	$987.54		$1,071.3495	$1,071.34	$1,071.25	$1,071.50