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	$239.73	5.362%	$252.5843	$252.58	$252.60	$252.60
Purchase #2	$248.37	12.443%	$279.2747	$279.27	$279.25	$279.30
Purchase #3	$150.78	3.764%	$156.4554	$156.46	$156.45	$156.50
Purchase #4	$221.62	11.778%	$247.7224	$247.72	$247.70	$247.70
Purchase #5	$66.89	7.150%	$71.6726	$71.67	$71.65	$71.70
Purchase #6	$196.76	7.289%	$211.1018	$211.10	$211.10	$211.10
Purchase #7	$13.85	5.440%	$14.6034	$14.60	$14.60	$14.60
7 purchase totals =	$1,138.00		$1,233.4146	$1,233.40	$1,233.35	$1,233.50