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	$78.50	5.509%	$82.8246	$82.82	$82.80	$82.80
Purchase #2	$214.67	12.603%	$241.7249	$241.72	$241.70	$241.70
Purchase #3	$70.77	5.395%	$74.588	$74.59	$74.60	$74.60
Purchase #4	$152.48	12.338%	$171.293	$171.29	$171.30	$171.30
Purchase #5	$249.88	13.712%	$284.1435	$284.14	$284.15	$284.10
Purchase #6	$28.88	7.384%	$31.0125	$31.01	$31.00	$31.00
Purchase #7	$86.63	5.177%	$91.1148	$91.11	$91.10	$91.10
7 purchase totals =	$881.81		$976.7013	$976.68	$976.65	$976.60