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	$162.94	3.271%	$168.2698	$168.27	$168.25	$168.30
Purchase #2	$77.42	11.536%	$86.3512	$86.35	$86.35	$86.40
Purchase #3	$143.75	6.269%	$152.7617	$152.76	$152.75	$152.80
Purchase #4	$53.48	7.430%	$57.4536	$57.45	$57.45	$57.50
Purchase #5	$6.87	4.341%	$7.1682	$7.17	$7.15	$7.20
Purchase #6	$132.96	13.671%	$151.137	$151.14	$151.15	$151.10
Purchase #7	$119.97	9.389%	$131.234	$131.23	$131.25	$131.20
7 purchase totals =	$697.39		$754.3755	$754.37	$754.35	$754.50