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	$176.81	5.481%	$186.501	$186.50	$186.50	$186.50
Purchase #2	$160.57	4.652%	$168.0397	$168.04	$168.05	$168.00
Purchase #3	$14.83	13.604%	$16.8475	$16.85	$16.85	$16.80
Purchase #4	$48.65	4.693%	$50.9331	$50.93	$50.95	$50.90
Purchase #5	$151.61	13.123%	$171.5058	$171.51	$171.50	$171.50
Purchase #6	$14.97	6.230%	$15.9026	$15.90	$15.90	$15.90
Purchase #7	$41.54	9.689%	$45.5648	$45.56	$45.55	$45.60
7 purchase totals =	$608.98		$655.2945	$655.29	$655.30	$655.20