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	$137.46	10.853%	$152.3785	$152.38	$152.40	$152.40
Purchase #2	$39.90	3.518%	$41.3037	$41.30	$41.30	$41.30
Purchase #3	$216.60	11.146%	$240.7422	$240.74	$240.75	$240.70
Purchase #4	$179.49	7.854%	$193.5871	$193.59	$193.60	$193.60
Purchase #5	$138.59	9.794%	$152.1635	$152.16	$152.15	$152.20
Purchase #6	$142.42	7.436%	$153.0104	$153.01	$153.00	$153.00
Purchase #7	$116.44	8.573%	$126.4224	$126.42	$126.40	$126.40
7 purchase totals =	$970.90		$1,059.6078	$1,059.60	$1,059.60	$1,059.60