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	$128.34	3.305%	$132.5816	$132.58	$132.60	$132.60
Purchase #2	$187.82	4.526%	$196.3207	$196.32	$196.30	$196.30
Purchase #3	$188.90	4.190%	$196.8149	$196.81	$196.80	$196.80
Purchase #4	$157.32	5.497%	$165.9679	$165.97	$165.95	$166.00
Purchase #5	$214.32	3.800%	$222.4642	$222.46	$222.45	$222.50
Purchase #6	$104.42	4.565%	$109.1868	$109.19	$109.20	$109.20
Purchase #7	$170.90	3.607%	$177.0644	$177.06	$177.05	$177.10
7 purchase totals =	$1,152.02		$1,200.4005	$1,200.39	$1,200.35	$1,200.50