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	$137.67	5.298%	$144.9638	$144.96	$144.95	$145.00
Purchase #2	$22.32	10.303%	$24.6196	$24.62	$24.60	$24.60
Purchase #3	$154.74	13.785%	$176.0709	$176.07	$176.05	$176.10
Purchase #4	$132.81	10.632%	$146.9304	$146.93	$146.95	$146.90
Purchase #5	$23.76	13.756%	$27.0284	$27.03	$27.05	$27.00
Purchase #6	$67.56	7.530%	$72.6473	$72.65	$72.65	$72.60
Purchase #7	$38.32	10.266%	$42.2539	$42.25	$42.25	$42.30
7 purchase totals =	$577.18		$634.5143	$634.51	$634.50	$634.50