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	$189.88	8.162%	$205.378	$205.38	$205.40	$205.40
Purchase #2	$144.87	12.381%	$162.8064	$162.81	$162.80	$162.80
Purchase #3	$181.31	9.466%	$198.4728	$198.47	$198.45	$198.50
Purchase #4	$73.82	10.670%	$81.6966	$81.70	$81.70	$81.70
Purchase #5	$139.43	7.760%	$150.2498	$150.25	$150.25	$150.20
Purchase #6	$93.70	12.150%	$105.0846	$105.08	$105.10	$105.10
Purchase #7	$167.82	11.510%	$187.1361	$187.14	$187.15	$187.10
7 purchase totals =	$990.83		$1,090.8243	$1,090.83	$1,090.85	$1,090.80