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	$91.43	9.814%	$100.4029	$100.40	$100.40	$100.40
Purchase #2	$99.53	5.656%	$105.1594	$105.16	$105.15	$105.20
Purchase #3	$147.87	4.709%	$154.8332	$154.83	$154.85	$154.80
Purchase #4	$176.61	12.602%	$198.8664	$198.87	$198.85	$198.90
Purchase #5	$116.54	8.600%	$126.5624	$126.56	$126.55	$126.60
Purchase #6	$122.39	3.290%	$126.4166	$126.42	$126.40	$126.40
Purchase #7	$197.37	3.247%	$203.7786	$203.78	$203.80	$203.80
7 purchase totals =	$951.74		$1,016.0195	$1,016.02	$1,016.00	$1,016.10