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	$215.60	13.853%	$245.4671	$245.47	$245.45	$245.50
Purchase #2	$94.30	11.611%	$105.2492	$105.25	$105.25	$105.20
Purchase #3	$210.51	13.513%	$238.9562	$238.96	$238.95	$239.00
Purchase #4	$216.55	6.842%	$231.3664	$231.37	$231.35	$231.40
Purchase #5	$100.87	9.666%	$110.6201	$110.62	$110.60	$110.60
Purchase #6	$208.87	13.743%	$237.575	$237.58	$237.60	$237.60
Purchase #7	$10.76	5.132%	$11.3122	$11.31	$11.30	$11.30
7 purchase totals =	$1,057.46		$1,180.5462	$1,180.56	$1,180.50	$1,180.60