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	$44.54	6.510%	$47.4396	$47.44	$47.45	$47.40
Purchase #2	$55.40	13.665%	$62.9704	$62.97	$62.95	$63.00
Purchase #3	$102.90	6.658%	$109.7511	$109.75	$109.75	$109.80
Purchase #4	$78.63	13.762%	$89.4511	$89.45	$89.45	$89.50
Purchase #5	$80.55	8.451%	$87.3573	$87.36	$87.35	$87.40
Purchase #6	$58.66	9.617%	$64.3013	$64.30	$64.30	$64.30
Purchase #7	$137.84	4.713%	$144.3364	$144.34	$144.35	$144.30
7 purchase totals =	$558.52		$605.6072	$605.61	$605.60	$605.70