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	$93.69	7.397%	$100.6202	$100.62	$100.60	$100.60
Purchase #2	$116.38	5.557%	$122.8472	$122.85	$122.85	$122.80
Purchase #3	$200.55	7.293%	$215.1761	$215.18	$215.20	$215.20
Purchase #4	$111.50	13.630%	$126.6975	$126.70	$126.70	$126.70
Purchase #5	$82.30	8.725%	$89.4807	$89.48	$89.50	$89.50
Purchase #6	$89.27	12.673%	$100.5832	$100.58	$100.60	$100.60
Purchase #7	$127.77	10.458%	$141.1322	$141.13	$141.15	$141.10
7 purchase totals =	$821.46		$896.5371	$896.54	$896.60	$896.50