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	$134.86	5.338%	$142.0588	$142.06	$142.05	$142.10
Purchase #2	$41.70	13.666%	$47.3987	$47.40	$47.40	$47.40
Purchase #3	$5.94	8.189%	$6.4264	$6.43	$6.45	$6.40
Purchase #4	$242.89	5.466%	$256.1664	$256.17	$256.15	$256.20
Purchase #5	$103.80	7.159%	$111.231	$111.23	$111.25	$111.20
Purchase #6	$88.86	10.819%	$98.4738	$98.47	$98.45	$98.50
Purchase #7	$220.39	10.861%	$244.3266	$244.33	$244.35	$244.30
7 purchase totals =	$838.44		$906.0817	$906.09	$906.10	$906.10