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	$206.71	3.694%	$214.3459	$214.35	$214.35	$214.30
Purchase #2	$111.94	7.587%	$120.4329	$120.43	$120.45	$120.40
Purchase #3	$245.86	9.421%	$269.0225	$269.02	$269.00	$269.00
Purchase #4	$66.82	5.556%	$70.5325	$70.53	$70.55	$70.50
Purchase #5	$132.85	10.640%	$146.9852	$146.99	$147.00	$147.00
Purchase #6	$13.83	4.557%	$14.4602	$14.46	$14.45	$14.50
Purchase #7	$184.88	6.258%	$196.4498	$196.45	$196.45	$196.40
7 purchase totals =	$962.89		$1,032.2290	$1,032.23	$1,032.25	$1,032.10