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	$90.38	9.405%	$98.8802	$98.88	$98.90	$98.90
Purchase #2	$67.49	7.538%	$72.5774	$72.58	$72.60	$72.60
Purchase #3	$89.78	8.124%	$97.0737	$97.07	$97.05	$97.10
Purchase #4	$92.93	8.388%	$100.725	$100.73	$100.75	$100.70
Purchase #5	$169.79	5.576%	$179.2575	$179.26	$179.25	$179.30
Purchase #6	$220.29	4.794%	$230.8507	$230.85	$230.85	$230.90
Purchase #7	$231.89	8.802%	$252.301	$252.30	$252.30	$252.30
7 purchase totals =	$962.55		$1,031.6655	$1,031.67	$1,031.70	$1,031.80