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	$131.93	7.354%	$141.6321	$141.63	$141.65	$141.60
Purchase #2	$224.71	12.654%	$253.1448	$253.14	$253.15	$253.10
Purchase #3	$38.34	12.844%	$43.2644	$43.26	$43.25	$43.30
Purchase #4	$113.80	8.550%	$123.5299	$123.53	$123.55	$123.50
Purchase #5	$158.94	13.609%	$180.5701	$180.57	$180.55	$180.60
Purchase #6	$145.69	10.348%	$160.766	$160.77	$160.75	$160.80
Purchase #7	$49.41	13.159%	$55.9119	$55.91	$55.90	$55.90
7 purchase totals =	$862.82		$958.8192	$958.81	$958.80	$958.80