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	$158.60	11.205%	$176.3711	$176.37	$176.35	$176.40
Purchase #2	$104.39	8.643%	$113.4124	$113.41	$113.40	$113.40
Purchase #3	$172.72	7.805%	$186.2008	$186.20	$186.20	$186.20
Purchase #4	$214.41	11.188%	$238.3982	$238.40	$238.40	$238.40
Purchase #5	$69.33	11.449%	$77.2676	$77.27	$77.25	$77.30
Purchase #6	$80.91	5.834%	$85.6303	$85.63	$85.65	$85.60
Purchase #7	$52.98	11.408%	$59.024	$59.02	$59.00	$59.00
7 purchase totals =	$853.34		$936.3044	$936.30	$936.25	$936.30