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	$215.37	8.704%	$234.1158	$234.12	$234.10	$234.10
Purchase #2	$11.78	13.632%	$13.3858	$13.39	$13.40	$13.40
Purchase #3	$107.72	7.775%	$116.0952	$116.10	$116.10	$116.10
Purchase #4	$131.63	8.495%	$142.812	$142.81	$142.80	$142.80
Purchase #5	$196.90	4.176%	$205.1225	$205.12	$205.10	$205.10
Purchase #6	$114.96	7.536%	$123.6234	$123.62	$123.60	$123.60
Purchase #7	$92.88	3.316%	$95.9599	$95.96	$95.95	$96.00
7 purchase totals =	$871.24		$931.1146	$931.12	$931.05	$931.10