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	$38.43	8.561%	$41.72	$41.72	$41.70	$41.70
Purchase #2	$82.52	8.238%	$89.318	$89.32	$89.30	$89.30
Purchase #3	$92.84	4.247%	$96.7829	$96.78	$96.80	$96.80
Purchase #4	$209.50	13.339%	$237.4452	$237.45	$237.45	$237.40
Purchase #5	$44.43	4.149%	$46.2734	$46.27	$46.25	$46.30
Purchase #6	$208.96	7.735%	$225.1231	$225.12	$225.10	$225.10
Purchase #7	$234.56	11.330%	$261.1356	$261.14	$261.15	$261.10
7 purchase totals =	$911.24		$997.7982	$997.80	$997.75	$997.70