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	$77.76	5.504%	$82.0399	$82.04	$82.05	$82.00
Purchase #2	$66.26	6.612%	$70.6411	$70.64	$70.65	$70.60
Purchase #3	$156.42	11.610%	$174.5804	$174.58	$174.60	$174.60
Purchase #4	$119.56	10.808%	$132.482	$132.48	$132.50	$132.50
Purchase #5	$175.92	11.850%	$196.7665	$196.77	$196.75	$196.80
Purchase #6	$56.44	11.204%	$62.7635	$62.76	$62.75	$62.80
Purchase #7	$181.44	5.139%	$190.7642	$190.76	$190.75	$190.80
7 purchase totals =	$833.80		$910.0376	$910.03	$910.05	$910.10