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	$83.55	4.778%	$87.542	$87.54	$87.55	$87.50
Purchase #2	$116.44	9.817%	$127.8709	$127.87	$127.85	$127.90
Purchase #3	$78.81	9.250%	$86.0999	$86.10	$86.10	$86.10
Purchase #4	$59.79	11.778%	$66.8321	$66.83	$66.85	$66.80
Purchase #5	$88.44	4.301%	$92.2438	$92.24	$92.25	$92.20
Purchase #6	$250.54	11.582%	$279.5575	$279.56	$279.55	$279.60
Purchase #7	$20.61	3.671%	$21.3666	$21.37	$21.35	$21.40
7 purchase totals =	$698.18		$761.5128	$761.51	$761.50	$761.50