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	$97.32	3.382%	$100.6114	$100.61	$100.60	$100.60
Purchase #2	$86.69	7.164%	$92.9005	$92.90	$92.90	$92.90
Purchase #3	$61.54	8.539%	$66.7949	$66.79	$66.80	$66.80
Purchase #4	$142.79	10.163%	$157.3017	$157.30	$157.30	$157.30
Purchase #5	$198.40	9.548%	$217.3432	$217.34	$217.35	$217.30
Purchase #6	$148.66	6.552%	$158.4002	$158.40	$158.40	$158.40
Purchase #7	$168.43	7.601%	$181.2324	$181.23	$181.25	$181.20
7 purchase totals =	$903.83		$974.5843	$974.57	$974.60	$974.50