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	$114.88	10.183%	$126.5782	$126.58	$126.60	$126.60
Purchase #2	$196.76	6.261%	$209.0791	$209.08	$209.10	$209.10
Purchase #3	$33.97	7.552%	$36.5354	$36.54	$36.55	$36.50
Purchase #4	$91.77	13.339%	$104.0112	$104.01	$104.00	$104.00
Purchase #5	$131.27	9.234%	$143.3915	$143.39	$143.40	$143.40
Purchase #6	$87.46	3.170%	$90.2325	$90.23	$90.25	$90.20
Purchase #7	$13.82	4.498%	$14.4416	$14.44	$14.45	$14.40
7 purchase totals =	$669.93		$724.2695	$724.27	$724.35	$724.20